1993 Jeep Cherokee

1993 ENGINE PERFORMANCE

Chrysler Corp 2 . 5L & 4.0L Self-Diagnostics

Jeep; Cherokee, Grand Cherokee, Wrangler

NOTE: For Grand Cherokee with 5.2L engine, see G - 5.2L TESTS W/ CODES article in the ENGINE PERFORMANCE Section.

INTRODUCTION

If no faults were found while performing F - 2.5L & 4.0L BASIC TESTING, proceed with self-diagnostics. If no fault codes or only pass codes are present after entering self-diagnostics, proceed to H - TESTS W/O CODES article in the ENGINE PERFORMANCE Section for diagnosis by symptom (i.e. ROUGH IDLE, NO START, etc.).

SYSTEM DIAGNOSTICS

NOTE: Malfunction Indicator Light (MIL) may also be referred to as CHECK ENGINE light.

The self-diagnostic capabilities of this system, if properly utilized, can simplify testing. The Powertrain Control Module (PCM) monitors several different engine control system circuits.

If a problem is sensed with a monitored circuit, PCM memory stores a fault, the MIL glows and PCM enters limp-in mode. In limp-in mode, PCM compensates for component failure by substituting information from other sources. This allows vehicle operation until repairs can be made.

Test circuits and repair or replace components as required. If problem is repaired or ceases to exist, the PCM cancels fault after 50 ignition on/off cycles.

A specific fault results from a particular system failure. A fault does not condemn a specific component; component is not necessarily the reason for failure. Faults only call out a probable malfunction area.

Hard Failures

Hard failures cause MIL to glow and remain on until the malfunction is repaired. If light comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined using self-diagnostic tests. If a sensor fails, PCM will use a substitute value in its calculations, allowing engine to operate in limp-in mode. In this condition, vehicle will run, but driveability may be poor.

Intermittent Failures

Intermittent failures may cause MIL to flicker or stay on until the intermittent fault goes away. However, the corresponding fault will be retained in PCM memory. If related fault does not reoccur within a certain time frame, related fault will be erased from PCM memory. Intermittent failures can be caused by a faulty sensor, bad connector or wiring related problems.

MODEL IDENTIFICATION

VEHICLE BODY IDENTIFICATION TABLE

Model Name Body Type

Cherokee XJ

Grand Cherokee ZJ

Wrangler YJ

SELF-DIAGNOSTIC SYSTEM

SERVICE PRECAUTIONS

Before proceeding with diagnosis, the following precautions must be followed:

65535. ALWAYS relieve fuel pressure before disconnecting any fuel
       injection-related component. DO NOT allow fuel to contact
       engine or electrical components. See FUEL PRESSURE RELEASE.

65536. When battery is disconnected, vehicle computer and memory
       systems may lose memory data. Driveability problems may exist
       until computer systems have completed a relearn cycle. See
       COMPUTER RELEARN PROCEDURES article in the GENERAL
       INFORMATION Section before disconnecting battery.

65537. Vehicle must have a fully charged battery and functional
       charging system.

65538. Probe PCM 60-pin connector from pin side. DO NOT backprobe
       PCM connector.

65539. DO NOT cause short circuits when performing electrical tests.
       This will set additional faults, making diagnosis of original
       problem more difficult.

65540. DO NOT use a test light instead of a voltmeter.

65541. When checking for spark, ensure coil wire is NO more than
       1/4" from ground. If coil wire is more than 1/4" from ground,
       damage to vehicle electronics and/or PCM may result.

65542. DO NOT prolong testing of fuel injectors or engine may
       hydrostatically (liquid) lock.

65543. Always repair lowest fault code number (MIL) or first fault
       displayed (DRB-II) first.

65544. Always perform verification test after repairs are made.

65545. Always disconnect DRB-II after use.

65546. Always disconnect DRB-II before charging battery.

FUEL PRESSURE RELEASE

WARNING: Always relieve fuel pressure before disconnecting any fuel injection-related component. DO NOT allow fuel to contact engine or electrical components.

CAUTION: When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in the GENERAL INFORMATION Section before disconnecting battery.

1. Disconnect negative battery cable. Slowly open fuel tank
   cap to release fuel tank pressure. Remove protective cap from pressure
   test port on fuel rail. See Fig. 1.

2. Using Fuel Pressure Gauge Tool Set (5069), obtain fuel
   pressure gauge and hose assembly. Remove gauge from hose. Place gauge
   end of hose in approved gasoline container. Place shop towel under
   test port. Screw other end of hose onto fuel pressure test port.
   Release fuel pressure. After pressure is released, remove hose from
   test port. Install protective cap on pressure test port.

3. If gauge tool set is not available, perform step 1). Using

a small screwdriver, wrapped in shop towels, push test port valve in to relieve fuel pressure. Absorb spilled fuel with shop towels. Remove shop towels and dispose of properly. Install protective cap on pressure test port.

_92A22483

Fig. 1: Releasing Fuel Pressure Courtesy of Chrysler Corp.

VISUAL INSPECTION

Most driveability problems in the engine control system result from faulty wiring, poor electrical connections or leaking air and vacuum hose connections. To avoid unnecessary component testing, perform a visual inspection before beginning self-diagnostic tests.

DIAGNOSTIC PROCEDURE

NOTE: DO NOT skip any steps in self-diagnostic tests or incorrect diagnosis may result.

Always perform a visual inspection before attempting to diagnose engine control system problems. See VISUAL INSPECTION. Enter on-board diagnostics, and retrieve fault code(s). See ENTERING ON­BOARD DIAGNOSTICS. If fault codes are not present and/or DRB-II (Diagnostic Readout Box II) is used, proceed to one of the following

tests:

65535. Go to TEST NS-1A (QUALIFYING NO START CONDITION) if a no
       start condition exists or engine stalls after start-up.
       Perform indicated VERIFICATION TEST after repairs have been
       made.

65536. Go to TEST FC-1A (CHECKING FOR FAULTS) if engine runs but has
       performance problems. Perform indicated VERIFICATION TEST
       after repairs have been made.

65537. Go to TEST NF-1A (NO FAULT TEST CODE MENU) if a driveability
       problem exits and no fault codes are present. Perform
       indicated VERIFICATION TEST after repairs have been made.

ENTERING ON-BOARD DIAGNOSTICS

NOTE: Although other scan testers are available, manufacturer recommends using DRB-II (Diagnostic Readout Box II) to diagnose the system. MIL function can be used but has limited diagnostic capability.

DRB-II Diagnostic Mode

4. Ensure ignition is off. Attach DRB-II to engine diagnostic
   connector. Connector is located on left side (right side on Grand
   Cherokee) of engine compartment, near PCM. See Figs. 2 and 3. Start
   engine (if possible). Turn A/C system on, then off (if equipped).

5. Turn engine off. Without starting engine, turn ignition on
   and access READ FAULTS function of DRB-II FUEL/IGN MENU.

6. Record all fault messages displayed by DRB-II, and observe
   MIL on instrument cluster. MIL should come on for 3 seconds and then
   go out (bulb check).

MIL Diagnostic Mode

1) Start engine (if possible). Move transmission shift lever
through all positions, ending in Park. Turn A/C switch on and then off

(if equipped).

7. Turn engine off. Without starting engine again, turn
   ignition on, off, on, off and on within 5 seconds. Record 2-digit
   fault codes as displayed by flashing MIL.

8. For example, fault code 23 is displayed as flash, flash,
   4-second pause, flash, flash, flash. After a slightly longer pause,
   other codes stored are displayed in numerical order. When MIL begins
   to flash fault codes, it cannot be stopped. Start over if count is
   lost. Code 55 indicates end of fault code display.

9. Refer to FAULT CODES/MESSAGE table to translate trouble
   code number to a DRB-II fault message. Once trouble area is
   identified, refer to TEST FC-1A. Use DRB-II fault messages to find
   appropriate test.

10. As an example, a 2.5L engine starts and runs but has a
    driveability problem. MIL indicates Code 14. Refer to FAULT
    CODES/MESSAGES to translate trouble code number to DRB-II fault
    message. When DRB-II fault message is obtained, refer to appropriate
    test number. To clear fault codes, see CLEARING FAULTS.

Fig. 2: Locating Diagnostic Connector (Cherokee & Wrangler) Courtesy of Chrysler Corp.

93F76211

CAUTION: When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in the GENERAL INFORMATION Section before disconnecting battery.

11. If DRB-II is not available, go to step 3). If DRB-II is
    available, press "1" key selecting FUEL/IGNITION. Press "2" key
    selecting READ FAULTS. Press down arrow key selecting next screen.
    Press "2" key selecting ERASE.

12. DRB-II will display ERASE FAULTS ARE YOU SURE? (ENTER TO
    ERASE). Press ENTER key. When DRB-II is finished erasing faults,
    screen will display FAULTS ERASED.

13. Fault codes may be cleared by disconnecting negative
    battery cable for at least 15 seconds, allowing PCM to clear faults.

INACTIVE FAULT CONDITION

This procedure applies if you have been sent here from diagnostic tests and have just attempted to simulate the condition that initially set the fault message. The following additional checks may assist in identifying a possible intermittent problem:

65535. Visually inspect related wiring harness connectors for
       broken, bent, pushed out or corroded terminals.

65536. Visually inspect related wiring harnesses for chafed, pierced
       or partially broken wires.

65537. Check all pertinent MITCHELL(R) TECH SERVICE BULLETINS
       (TSBs) .

USING DRB-II

NOTE: Although other scan testers are available, manufacturer recommends using DRB-II (Diagnostic Readout Box II) to diagnose the system.

Ensure DRB-II is connected to engine diagnostic connector located in engine compartment. Ensure correct cartridge is installed in DRB-II for vehicle and system being diagnosed. Menu selections will vary depending on vehicle and system being diagnosed. Follow DRB-II screen prompts to actuate, adjust, monitor, reset, test and diagnose system as necessary.

DRB-II is grounded through engine diagnostic connector. Only one volt-ohmmeter test lead is required when using volt-ohmmeter option. DRB-II volt-ohmmeter should only be used when self-diagnostic tests require the use of this option.

If DRB-II has a blank screen or displays RAM TEST FAILURE, CARTRIDGE ERROR, KEY PAD TEST FAILURE or LOW BATTERY OR HIGH BATTERY, this indicates a DRB-II failure. To diagnose and correct these conditions, see G - BODY TESTS W/ CODES article in the ENGINE PERFORMANCE Section.

SERVICE REMINDER INDICATOR (SRI) MEMORY TEST

NOTE: Perform SRI memory test only if referred here by diagnostic tests.

1) To perform SRI memory check, ensure ignition is off. Attach DRB-II to engine diagnostic connector. Connector is located on left side (right side on Grand Cherokee) of engine compartment, near PCM. See Figs. 2 and 3. Turn ignition switch to RUN position.

2) Copyright information and diagnostic program version will
appear on screen for a few seconds. After a few seconds DRB-II menu
will appear. At FUEL/IGN MENU, press "5" (ADJUSTMENTS) key. Press
ENTER key. At ADJUSTMENTS menu, press "4" (SRI MEMORY CHK) key. Press
ENTER key. The DRB-II display will read SRI MEMORY CHECK ARE YOU SURE?

(ENTER TO CONTINUE).

3) Press ENTER key. The DRB-II will display SRI MEMORY TEST

WRITE TEST [ ] and after a few seconds IS INSTRUMENT PANEL

MILEAGE BETWEEN XXXXX AND XXXXX? (PRESS YES OR NO). If vehicle mileage is within specification, SRI memory check is complete. Press YES key. If vehicle mileage is not within specification, go to next step.

14. Press NO key. DRB-II will display ENTER MILEAGE SHOWN ON
    INSTRUMENT PANEL (USE ENTER TO END) XXXXXXX. Enter vehicle mileage. DO
    NOT enter tenths. When correct vehicle mileage is entered, press ENTER
    key.

15. DRB-II will ask for verification of mileage entry. If
    mileage entry was accurate, press ENTER key. DRB-II will display SRI
    MEMORY CHECK COMPLETE. Vehicle must travel at least 8 miles for reset
    to occur.

SERVICE REMINDER INDICATOR (SRI) LIGHT RESET PROCEDURE

Service Reminder Indicator (SRI) light is designed to be a reminder to service vehicle emissions control system. It is not an emissions warning system, only a reminder to perform necessary emissions servicing.

Components to be serviced include PCV valve, oxygen sensor and some vacuum-operated components. SRI light will illuminate after a predetermined mileage.

1) To reset SRI light, ensure ignition is off. Connect DRB-II
to engine diagnostic connector. Connector is located on left side

(right side on Grand Cherokee) of engine compartment, near PCM. See Figs. 2 and 3. Turn ignition switch to RUN position.

16. Copyright information and diagnostic program version will
    appear on screen for a few seconds. After a few seconds, DRB-II menu
    will appear. At FUEL/IGN MENU, press "5" (ADJUSTMENTS) key. Press
    ENTER key.

17. At ADJUSTMENTS menu, press "3" (RESET SRI LIGHT) key.
    Press ENTER key. Display will read RESET SRI LIGHT ARE YOUR SURE?

(ENTER TO RESET). Press ENTER key.

SERVICE REMINDER INDICATOR (SRI) MILEAGE TRANSFER

NOTE: Perform mileage transfer procedure only if PCM is being replaced.

18. When PCM is replaced, vehicle mileage must be copied from
    odometer to replacement PCM memory. Transfer of vehicle mileage will
    enable new PCM to operate SRI light properly.

19. To transfer mileage to new PCM, ensure ignition is off.
    Connect DRB-II to engine diagnostic connector. Connector is located on
    left side (right side on Grand Cherokee) of engine compartment, near
    PCM. See Figs. 2 and 3. Turn ignition switch to RUN position.

20. Copyright information and diagnostic program version will
    appear on screen for a few seconds. After a few seconds DRB-II menu
    will appear. At FUEL/IGN MENU, press "5" (ADJUSTMENTS) key. Press
    ENTER key. At ADJUSTMENTS menu, press "4" (SRI MEMORY CHK) key. Press
    ENTER key. The DRB-II display will read SRI MEMORY CHECK ARE YOU SURE?

(ENTER TO CONTINUE).

4) Press ENTER key. The DRB-II will display SRI MEMORY TEST

WRITE TEST [ ] and after a few seconds IS INSTRUMENT PANEL

MILEAGE BETWEEN XXXXX AND XXXXX? (PRESS YES OR NO). If vehicle mileage is within specification, SRI memory check is complete. Press YES key.

If vehicle mileage is not within specification, go to next step.

21. Press NO key. DRB-II will display ENTER MILEAGE SHOWN ON
    INSTRUMENT PANEL (USE ENTER TO END) XXXXXXX. Enter vehicle mileage. DO
    NOT enter tenths. When correct vehicle mileage is entered, press ENTER
    key.

22. DRB-II will ask for verification of mileage entry. If
    mileage entry was accurate, press ENTER key. DRB-II will display SRI
    MEMORY CHECK COMPLETE. Vehicle must travel at least 8 miles for reset
    to occur.

THEFT ALARM SYSTEM

NOTE: If SECURITY light comes on and remains on with ignition on, Chrysler Collision Detection (CCD) bus communication with PCM has been lost. After servicing vehicle, ensure system operates properly. A malfunctioning anti-theft alarm system may keep engine from starting. For anti-theft alarm diagnosis, see appropriate ANTI-THEFT SYSTEM article in the ACCESSORIES/SAFETY EQUIPMENT Section.

FAULT CODES/MESSAGES

NOTE: Not all fault codes apply to all vehicles. Some fault codes have more than one meaning. When a fault code has more than one meaning, MIL is unable to distinguish between different failures.

Code 11

DRB-II displays NO CRANK REFERENCE SIGNAL AT PCM. Condition is: no crankshaft reference signal picked up during cranking.

Code 13

DRB-II displays SLOW CHANGE IN IDLE MAP SENSOR SIGNAL. Condition is: Manifold Absolute Pressure (MAP) sensor output change slower and/or smaller than expected.

Code 13

DRB-II displays NO CHANGE IN MAP FROM START TO RUN. Condition is: no difference recognized between Manifold Absolute Pressure (MAP) reading and barometric (atmospheric) pressure reading at start-up.

Code 14

DRB-II displays MAP VOLTAGE TOO LOW. Condition is: Manifold Absolute Pressure (MAP) sensor input less than minimum acceptable voltage.

Code 14

DRB-II displays MAP VOLTAGE TOO HIGH. Condition is: Manifold Absolute Pressure (MAP) sensor input more than maximum acceptable voltage.

Code 15

DRB-II displays NO VEHICLE SPEED SENSOR SIGNAL. Condition is: no Vehicle Speed Sensor (VSS) signal detected with road load conditions.

Code 17

DRB-II displays ENGINE IS COLD TOO LONG. Condition is: coolant temperature stays less than normal operating temperature during vehicle operation.

Code 21

DRB-II displays O2S STAYS AT CENTER. Condition is: no rich or lean signal detected from oxygen sensor input.

Code 21

DRB-II displays O2S SHORTED TO VOLTAGE. Condition is: oxygen sensor input voltage maintained at more than normal operating range.

Code 22

DRB-II displays ECT SENSOR VOLTAGE TOO LOW. Condition is: Engine Coolant Temperature (ECT) sensor input less than minimum acceptable voltage.

Code 22

DRB-II displays ECT SENSOR VOLTAGE TOO HIGH. Condition is: Engine Coolant Temperature (ECT) sensor input more than maximum acceptable voltage.

Code 23

DRB-II displays INTAKE AIR TEMPERATURE SENSOR VOLTAGE LOW. Condition is: Intake Air Temperature (IAT) sensor input less than minimum acceptable voltage.

Code 23

DRB-II displays INTAKE AIR TEMPERATURE SENSOR VOLTAGE HIGH. Condition is: Intake Air Temperature (IAT) sensor input more than maximum acceptable voltage.

Code 24

DRB-II displays THROTTLE POSITION SENSOR VOLTAGE LOW.

Condition is: Throttle Position Sensor (TPS) input less than minimum acceptable voltage.

Code 24

DRB-II displays THROTTLE POSITION SENSOR VOLTAGE HIGH. Condition is: Throttle Position Sensor (TPS) input more than maximum acceptable voltage.

Code 25

DRB-II displays IDLE AIR CONTROL MOTOR CIRCUITS. Condition is: open or shorted condition detected in one or more Idle Air Control (IAC) motor circuits.

Code 27

DRB-II displays INJECTOR #1-6 CONTROL CIRCUIT. Condition is: injector output driver does not respond properly to Powertrain Control Module (PCM) control signal.

Code 33

DRB-II displays A/C CLUTCH RELAY CIRCUIT. Condition is: open or shorted condition detected in A/C clutch relay circuit.

Code 34

DRB-II displays SPEED CONTROL SOLENOID CIRCUITS. Condition is: open or shorted condition detected in Speed Control (S/C) vacuum or vent solenoid circuits.

Code 35

DRB-II displays RADIATOR FAN RELAY CIRCUIT. Condition is: open or shorted condition detected in radiator fan relay circuit.

Code 41

DRB-II displays GENERATOR FIELD NOT SWITCHING PROPERLY. Condition is: open or shorted condition detected in alternator field

circuit.

Code 42

DRB-II displays AUTO SHUTDOWN RELAY CONTROL CIRCUIT. Condition is: open or shorted condition detected in Auto Shutdown (ASD) relay circuit.

Code 42

DRB-II displays NO ASD RELAY VOLTAGE SENSE AT PCM. Condition is: Powertrain Control Module (PCM) did not receive message in Auto Shutdown (ASD) relay circuit.

Code 44

DRB-II displays BATTERY TEMP SENSOR VOLTS OUT OF LIMIT. Condition is: Powertrain Control Module (PCM) failure.

Code 4 6

DRB-II displays CHARGING SYSTEM VOLTAGE TOO HIGH. Condition is: battery voltage sense input more than target charging voltage during engine operation.

Code 47

DRB-II displays CHARGING SYSTEM VOLTAGE TOO LOW. Condition is: battery voltage sense input less than target charging voltage during engine operation.

Code 51

DRB-II displays O2S STAYS BELOW CENTER (LEAN). Condition is: oxygen sensor input indicates lean air/fuel ratio during engine operation.

Code 52

DRB-II displays O2S STAYS ABOVE CENTER (RICH). Condition is: oxygen sensor input indicates rich air/fuel ratio during engine operation.

Code 53

DRB-II displays INTERNAL PCM FAILURE. Condition is: Powertrain Control Module (PCM) detects internal failure.

Code 53

DRB-II displays PCM FAILURE SPI COMMUNICATION. Condition is: No CCD bus communication.

Code 54

DRB-II displays NO CAM SYNC SIGNAL AT PCM. Condition is: open or shorted condition detected in cam sync signal circuit.

Code 55

DRB-II display will be blank. Completion of fault code display by CHECK ENGINE light.

Code 62

DRB-II displays PCM FAILURE SRI MILE NOT STORED. Condition is: Powertrain Control Module (PCM) detects internal failure.

Code 63

DRB-II displays PCM FAILURE EEPROM WRITE DENIED. Condition is: unsuccessful attempt to write to an EEPROM location by PCM.

Code 7 6

DRB-II displays FUEL PUMP RESISTOR BY-PASS RELAY CIRCUIT. Condition is: open or shorted condition detected in ballast resistor

by-pass relay circuit.

CAUTION: When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in the GENERAL INFORMATION Section before disconnecting battery.

CONNECTOR IDENTIFICATION

CONNECTOR IDENTIFICATION DIRECTORY TABLE

Connector See Fig.

Idle Air Control (IAC) Motor 4

Coolant Temperature Sensor 5

Camshaft & Crankshaft Position Sensor 6

Engine Controller 7

Engine Diagnostic 8

Fuel Injector 9

Ignition Coil 10

Manifold Absolute Pressure (MAP) Sensor 11

Oxygen (O2) Sensor 12

Relays 13

Throttle Position Sensor 14

Fuel Pump Relay Test 15

_92Е04769

_92104785

Fig. 7: Identifying Engine Controller Connector Terminals Courtesy of Chrysler Corp.

ENGINE DIAGNOSTIC CONNECTOR TERMINAL IDENTIFICATION

Cavity It Model Wire Color

No. 1

Cherokee (XJ) Black/White

Grand Cherokee (ZJ) В1аскДап

Wrangler (YJ) Black/White

No. 2 Not Used

No. 3

Cherokee (XJ) Pink

Grand Cherokee (ZJ) Black

Wrangler (YJ) Pink

No. 4

Cherokee (XJ) Light Green

Grand Cherokee (ZJ) Black/Yellow

Wrangler (YJ) Light Green

No.5

Cherokee (XJ) Dark Blue/White

Grand Cherokee (ZJ) Light Blue/Red

Wrangler (YJ) White/Yellow

No. 6 Not Used

93А7621Й

Fig. 8: Identifying Engine Diagnostic Connector Terminals Courtesy of Chrysler Corp.

ENGINE DIAGNOSTIC CONNECTOR TERMINAL IDENTIFICATION

Cavity & Model Wire Color

No. 1

Cherokee (XJ) Black/White

Grand Cherokee (ZJ) Black/Tan

Wrangler (YJ) Black/White

No. 2 Not Used

No. 3

Cherokee (XJ) Pink

Grand Cherokee (ZJ) Black

Wrangler (YJ) Pink

No. 4

Cherokee (XJ) Light Green

Grand Cherokee (ZJ) Black/Yellow

Wrangler (YJ) Light Green

No. 5

Cherokee (XJ) Dark Blue/White

Grand Cherokee (ZJ) Light Blue/Red

Wrangler (YJ) White/Yellow

Fig. 9: Identifying Fuel Injector Connector Terminals Courtesy of Chrysler Corp.

No. 6 Not Used

92E22487

Fig. 11: Manifold Absolute Pressure Courtesy of Chrysler Corp.

(MAP) Sensor Connector Term. ID

_92J04781

_92С04787

Fig. 14: Identifying Throttle Position Sensor Connector Terminals Courtesy of Chrysler Corp.

Fig. 15: Testing Fuel Pump Relay Courtesy of Chrysler Corp.

SELF-DIAGNOSTIC TESTS

NOTE: For Grand Cherokee with 5.2L engine, see G - 5.2L TESTS W/ CODES article in the ENGINE PERFORMANCE Section.

TEST FC-1A - CHECKING FOR FAULTS

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

1) Battery must be fully charged before proceeding. Attempt
to start engine. If engine will not start, crank engine for at least

23. seconds. Connect DRB-II to engine diagnostic connector. Record DRB-

24. fault messages.

25. If DRB-II has a blank screen or displays RAM TEST FAILURE,
    CARTRIDGE ERROR, KEY PAD TEST FAILURE, or LOW OR HIGH BATTERY, DRB-II
    failure is indicated. To diagnose and correct, see G - BODY TESTS W/
    CODES article in the ENGINE PERFORMANCE Section.

26. If DRB-II displays NO RESPONSE, go to TEST NS-6A. If fault
    messages are displayed, see DRB-II FAULT MESSAGES table. If no fault
    messages are displayed and a driveability problem is present, go to
    TEST NF-1A. If no fault messages are displayed and a no-start problem
    is present, go to TEST NS-1A.

DRB-II FAULT MESSAGES TABLE

DRB-II Message Test No.

NO CRANK REFERENCE SIGNAL AT PCM FC-2A

NO CAM SYNC SIGNAL AT PCM FC-3A

NO CHANGE IN MAP FROM START TO RUN FC-4A

MAP SENSOR VOLTAGE TOO LOW FC-5A

MAP SENSOR VOLTAGE TOO HIGH FC-6A

NO VEHICLE SPEED SENSOR SIGNAL FC-7A

O2S STAYS AT CENTER FC-8A

O2S SHORTED TO VOLTAGE FC-9A

O2S STAYS ABOVE CENTER (RICH) FC-10A

O2S STAYS BELOW CENTER (LEAN) FC-11A

ЕСТ SENSOR VOLTAGE TOO HIGH FC-12A

ЕСТ SENSOR VOLTAGE TOO LOW FC-13A

INTAKE AIR TEMP SENSOR VOLTAGE LOW FC-14A

INTAKE AIR TEMP SENSOR VOLTAGE HIGH FC-15A

THROTTLE POSITION SENSOR VOLTAGE HIGH FC-16A

THROTTLE POSITION SENSOR VOLTAGE LOW FC-17A

IDLE AIR CONTROL MOTOR CIRCUITS FC-18A

INJECTOR #1 CONTROL CIRCUIT FC-19A

INJECTOR #2 CONTROL CIRCUIT FC-20A

INJECTOR #3 CONTROL CIRCUIT FC-21A

INJECTOR #4 CONTROL CIRCUIT FC-22A

INJECTOR #5 CONTROL CIRCUIT FC-23A

INJECTOR #6 CONTROL CIRCUIT FC-24A

A/C CLUTCH RELAY CIRCUIT FC-25A

RAD FAN CONTROL RELAY CIRCUIT FC-26A

AUTO SHUTDOWN RELAY CONTROL CIRCUIT FC-27A

NO ASD RELAY VOLT SENSE AT PCM FC-28A

PCM FAILURE SRI MILE NOT STORED FC-2 9A

PCM FAILURE EEPROM WRITE DENIED FC-30A

FUEL PUMP RESISTOR BYPASS RELAY CIRCUIT FC-31A

CHARGING SYSTEM VOLTAGE TOO LOW (1)

CHARGING SYSTEM VOLTAGE TOO HIGH (1)

GENERATOR FIELD NOT SWITCHING PROPERLY (1)

ENGINE IS COLD TOO LONG (2 )

INTERNAL PCM FAILURE (3)

SPEED CONTROL SOLENOID CIRCUITS (4)

27. - See ALTERNATORS article in the ELECTRICAL Section.

28. - Check cooling system if engine temperature does not reach 176F

(80C) after driving 20 minutes. This code may set in error during very cold slow speed driving.

29. - Replace PCM and perform TEST VER-1.

30. - See CRUISE CONTROL SYSTEMS article the in ACCESSORIES/SAFETY

EQUIPMENT Section.

TEST FC-2A - NO CRANK REFERENCE SIGNAL AT PCM

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of this article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

31. Using DRB-II, erase fault messages. Attempt to start
    engine. If engine will not start, crank engine for at least 10
    seconds.

32. Using DRB-II, read fault messages. If DRB-II does not
    display NO CRANK REFERENCE SIGNAL AT PCM, condition required to set
    fault is not present at this time. Go to next step. If DRB-II displays
    NO CRANK REFERENCE SIGNAL AT PCM, go to step 6).

33. NO CRANK REFERENCE SIGNAL AT PCM fault sets if Powertrain
    Control Module (PCM) does not see a Crankshaft Position (CKP) sensor
    signal with Camshaft Position (CMP) sensor signal present. Possible
    causes are: failed CKP sensor, open or shorted CKP sensor signal
    circuit (Gray/Black wire on XJ and YJ bodies or Red/Light Green wire
    on ZJ body), open or shorted CKP sensor 8-volt supply circuit (Orange
    wire on XJ and YJ bodies or White/Black wire on ZJ body), open CKP
    sensor ground circuit (Black/Light Blue wire), improperly adjusted CKP
    sensor or failed Powertrain Control Module (PCM). Go to next step.

34. Inspect all related wiring and connectors and repair as
    necessary. Perform TEST VER-1. If no problems were found with wiring
    and connectors, go to next step.

35. Start engine. Wiggle wiring harness from CKP sensor to
    Powertrain Control Module (PCM). If engine misfires or stalls, repair
    wiring harness as necessary. Perform TEST VER-1. If engine does not
    misfire or stall, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

36. Turn ignition off. Disconnect Crankshaft Position (CKP)
    sensor connector. Using DRB-II in ohmmeter mode, check resistance of
    CKP sensor connector, 8-volt supply circuit (Orange wire on XJ and YJ
    bodies or White/Black wire on ZJ body). If resistance is less than 5
    ohms, repair short to ground in Orange wire on XJ and YJ bodies or
    White/Black wire on ZJ body.

37. If resistance is more than 5 ohms, turn ignition on. Using
    DRB-II in voltmeter mode, check voltage on CKP sensor connector, 8-
    volt supply circuit (Orange wire on XJ and YJ bodies or White/Black
    wire on ZJ body). If voltage is less than 7 volts, go to TEST FC-2B.
    If voltage is more than 7 volts, turn ignition off.

38. Connect a jumper wire between signal circuit (Gray/Black
    wire on XJ and YJ bodies or Red/Light Green wire on ZJ body) and
    ground circuit (Black/Light Blue wire) on CKP sensor connector harness
    side. Using DRB-II, read fault messages. Make and break connection at
    CKP sensor connector several times while observing DRB-II.

39. If DRB-II displays NO CAM SYNC SIGNAL AT PCM, replace CKP
    sensor. Perform TEST VER-1. If DRB-II does not display NO CAM SYNC
    SIGNAL AT PCM, turn ignition off.

10) Using DRB-II in ohmmeter mode, check resistance on CKP
sensor connector, ground circuit (Black/Light Blue wire). If

resistance is more than 5 ohms, repair open in Black/Light Blue wire. Perform TEST VER-1.

40. If resistance is less than 5 ohms, disconnect PCM
    connector. Inspect PCM sensor connector for damaged or pushed-out
    terminals. Repair as necessary. Perform TEST VER-1. If PCM connector
    terminals are okay, go to next step.

41. Using an external ohmmeter, check resistance of signal
    circuit(Gray/Black wire on XJ and YJ bodies or Red/Light Green wire on
    ZJ body) between CKP sensor connector harness side and PCM connector
    terminal No. 24. If resistance is more than 5 ohms, repair open in
    Gray/Black wire on XJ and YJ bodies or Red/Light Green wire on ZJ
    body. Perform TEST VER-1.

42. If resistance is less than 5 ohms, put DRB-II in ohmmeter
    mode. Using DRB-II, check resistance of CKP signal circuit (Gray/Black
    wire on XJ and YJ bodies or Red/Light Green wire on ZJ body) on PCM
    connector terminal No. 24. If resistance is more than 5 ohms, replace
    PCM. Perform TEST VER-1.

43. If resistance is less than 5 ohms, disconnect Camshaft
    Position (CMP) sensor connector. Using DRB-II, check resistance of CKP
    signal circuit (Gray/Black wire on XJ and YJ bodies or Red/Light Green
    wire on ZJ body) on PCM connector terminal No. 24. If resistance is
    less more than 5 ohms, replace CMP sensor. Perform TEST VER-1.

44. If resistance is less than 5 ohms, disconnect Vehicle
    Speed Sensor (VSS) connector. Using DRB-II, check resistance of CKP
    signal circuit (Gray/Black wire on XJ and YJ bodies or Red/Light Green
    wire on ZJ body) on PCM connector terminal No. 24. If resistance is
    more than 5 ohms, replace Vehicle Speed Sensor (VSS). Perform TEST
    VER-1. If resistance is less than 5 ohms, repair short to ground in
    Gray/Black wire on XJ and YJ bodies or Red/Light Green wire on ZJ
    body. Perform TEST VER-1.

TEST FC-2B - NO CRANK REFERENCE SIGNAL AT PCM

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

1) Turn ignition off. Disconnect Powertrain Control Module
(PCM) connector. Inspect PCM connector for damaged or pushed-out

terminals. Repair as necessary. Perform TEST VER-1. If PCM connector terminals are okay, go to next step.

2) Using an external ohmmeter, check resistance of 8-volt
supply circuit (Orange wire on XJ and YJ bodies or White/Black wire on
ZJ body) between CKP sensor connector harness side and PCM connector
terminal No. 7. If resistance is more than 5 ohms, repair open in
Orange wire on XJ and YJ bodies or White/Black wire on ZJ body.
Perform TEST VER-1. If resistance is less than 5 ohms, replace PCM.
Perform TEST VER-1.

TEST FC-3A - NO CAM SYNC SIGNAL AT PCM

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

45. Using DRB-II, erase fault messages. Attempt to start
    engine. If engine will not start, crank engine for at least 10
    seconds.

46. Using DRB-II, read fault messages. If DRB-II does not
    display NO CAM SYNC SIGNAL AT PCM, condition required to set fault is
    not present at this time. Go to next step. If DRB-II displays NO CAM

SYCN SIGNAL AT PCM, go to step 5).

47. NO CAM SYNC SIGNAL AT PCM fault sets if Powertrain Control
    Module does not see Camshaft Position (CMP) sensor signal with
    Crankshaft Position (CKP) signal present. Possible causes are: failed
    CMP sensor, open or shorted CMP sensor signal circuit (Tan/Yellow wire
    on XJ and YJ bodies or Gray/Black wire on ZL body), open CMP sensor 8-
    volt supply circuit (Orange wire on XJ and YJ bodies or White/Black
    wire on ZJ body), open CMP sensor ground circuit (Black/Light Blue
    wire), improperly adjusted CMP sensor or failed Powertrain Control
    Module (PCM). Go to next step.

48. Inspect all related wiring and connectors and repair as
    necessary. Perform TEST VER-1. If no problems were found with wiring
    or connectors, see INACTIVE FAULT CONDITION. Perform TEST VER-1. Go to
    next step.

49. Turn ignition off. Disconnect Camshaft Position (CMP)
    sensor connector. Using DRB-II in ohmmeter mode, check resistance of
    CMP sensor connector, 8-volt supply circuit (Orange wire on XJ and YJ
    bodies or White/Black wire on ZJ body). If resistance is less than 5
    ohms, repair short to ground in Orange wire on XJ and YJ bodies or
    White/Black wire on ZJ body. Perform TEST VER-1.

50. If resistance is more than 5 ohms, turn ignition on. Using
    DRB-II in voltmeter mode, check voltage on CMP sensor connector, 8-
    volt supply circuit (Orange wire on XJ and YJ bodies or White/Black
    wire on ZJ body). If voltage is less than 7 volts, go to TEST FC-3B.

51. If voltage is more than 7 volts, turn ignition off.
    Connect a jumper wire between signal circuit (Tan/Yellow wire on XJ
    and YJ bodies or Gray/Black wire on ZJ body) and ground circuit
    (Black/Light Blue wire) on CKP sensor connector harness side. Make and

break connection at CKP sensor connector several times.

52. Attempt to start engine. If engine starts, replace CMP
    sensor. Perform TEST VER-1. If engine does not start, turn ignition
    off.

53. Using DRB-II in ohmmeter mode, check resistance on CMP
    sensor connector, ground circuit (Black/Light Blue wire). If
    resistance is more than 5 ohms, repair open in Black/Light Blue wire.
    Perform TEST VER-1.

54. If resistance is less than 5 ohms, disconnect Powertrain
    Control Module (PCM) connector. Inspect PCM connector for damaged or
    pushed-out terminals. Repair as necessary. Perform TEST VER-1. If PCM
    connector terminals are okay, go to next step.

55. Using an external ohmmeter, check resistance of signal
    circuit(Tan/Yellow wire on XJ and YJ bodies or Gray/Black on ZJ body)
    between CMP sensor connector harness side and PCM connector terminal
    No. 44. If resistance is more than 5 ohms, repair open in Tan/Yellow
    wire on XJ and YJ bodies or Gray/Black on ZJ body. Perform TEST VER-1.

56. If resistance is less than 5 ohms, using DRB-II in
    ohmmeter mode, check resistance of PCM connector terminal No. 44. If
    resistance is more than 5 ohms, replace PCM. Perform TEST VER-1. If
    resistance is less than 5 ohms, repair short to ground in Tan/Yellow
    wire on XJ and YJ bodies or Gray/Black wire on ZJ body. Perform TEST
    VER-1.

TEST FC-3B - NO CAM SYNC SIGNAL AT PCM

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

1) Turn ignition off. Disconnect Powertrain Control Module (PCM) connector. Inspect PCM connector for damaged or pushed-out terminals. Repair as necessary. Perform TEST VER-1. If PCM connector terminals are okay, go to next step.

2) Using an external ohmmeter, check resistance of 8-volt supply circuit (Orange wire on XJ and YJ bodies or White/Black wire on ZJ body) between CMP sensor connector harness side and PCM connector terminal No. 7. If resistance is more than 5 ohms, repair open in Orange wire on XJ and YJ bodies or White/Black wire on ZJ body. Perform TEST VER-1. If resistance is less than 5 ohms, replace PCM. Perform TEST VER-1.

TEST FC-4A - NO CHANGE IN MAP FROM START TO RUN

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

57. Turn ignition on. Using DRB-II, erase fault messages.
    Start engine. Allow engine to idle for 30 seconds. With engine
    running, read fault messages using DRB-II. If DRB-II does not display
    NO CHANGE IN MAP FROM START TO RUN, go to step 4).

58. If DRB-II displays NO CHANGE IN MAP FROM START TO RUN,
    turn ignition off. Disconnect Manifold Absolute Pressure (MAP) sensor
    connector. Turn ignition on. Using DRB-II in voltmeter mode, check
    voltage on MAP sensor connector, 5-volt supply circuit (Violet/White
    wire).

59. If voltage is less than 4 volts, repair open or short in
    Violet/White wire. Perform TEST VER-1. If voltage is more than 4
    volts, remove MAP sensor vacuum hose. Inspect condition of MAP sensor
    vacuum hose. If MAP sensor vacuum hose is restricted or open, replace
    vacuum hose as necessary. Perform TEST VER-1. If MAP sensor vacuum
    hose is okay, replace MAP sensor. Perform TEST VER-1.

60. Using DRB-II, set engine speed to 1500 RPM. With engine
    running at 1500 RPM, read DRB-II MAP sensor voltage. While monitoring
    MAP sensor voltage, wiggle MAP sensor connector and wiring harness.

61. If engine stalls or MAP sensor voltage becomes erratic,
    inspect all related wiring and connectors and repair as necessary.
    Perform TEST VER-1. If engine does not stall and MAP sensor voltage
    does not become erratic, snap throttle open and closed while
    monitoring DRB-II.

62. If engine vacuum does not rapidly drop to less than one
    in. Hg, go to step 8). If engine vacuum rapidly drops to less than one
    in. Hg, condition required to set fault is not present at this time.
    Go to next step.

63. NO CHANGE IN MAP FROM START TO RUN fault sets if too small
    a difference is seen between barometric pressure at key on and
    manifold vacuum after engine start. Possible causes are: restricted or
    leaking vacuum/pressure hose to MAP sensor, ice in MAP sensor or
    passage, or MAP sensor failure. Perform TEST VER-1.

64. Remove MAP sensor vacuum hose. Inspect condition of MAP
    sensor vacuum hose. If MAP sensor vacuum hose is restricted or open,
    replace vacuum hose as necessary. Perform TEST VER-1. If MAP sensor
    vacuum hose is okay, replace MAP sensor. Perform TEST VER-1.

TEST FC-5A - MAP SENSOR VOLTAGE TOO LOW

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

1) Start engine. Using DRB-II, read Manifold Absolute Pressure (MAP) sensor voltage. If MAP sensor voltage is less than .2 volt, go to step 5). If MAP sensor voltage is more than .2 volt, turn engine off. Turn ignition on.

65. Using DRB-II, read MAP sensor voltage. If voltage is less
    than 1.2 volts, go to step 5). If voltage is more than 1.2 volts,
    wiggle MAP sensor connector and wiring harness while watching DRB-II
    display. If MAP sensor voltage changes, repair connector or wiring
    harness as necessary. Perform TEST VER-1.

66. If MAP sensor voltage does not change, condition required
    to set fault is not present at this time. MAP SENSOR VOLTAGE TOO LOW
    fault sets if MAP sensor output is less than 1.2 volts at start or
    less than .2 volt with engine running. Engine speed must be more than
    400 RPM, but less than 1500 RPM, and Throttle Position Sensor (TPS)
    voltage must be less than one volt. Possible causes are: short to
    ground in MAP sensor signal circuit (Dark Green/Red wire on XJ and YJ
    bodies or Red/White wire on ZJ body), MAP sensor shorted internally or
    loss of MAP sensor 5-volt supply circuit (Violet/White wire). Go to
    next step.

67. Inspect all related wiring and connectors and repair as
    necessary. Perform TEST VER-1. If no problems were found with wiring
    and connectors, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

68. Turn ignition on. Ensure engine is off. Disconnect MAP
    sensor connector. Using DRB-II, read MAP sensor voltage. If MAP sensor
    voltage is more than 4 volts, replace MAP sensor. Perform TEST VER-1.

69. If MAP sensor voltage is less than 4 volts, turn ignition
    off. Disconnect Powertrain Control Module (PCM) connector. Using DRB-
    II in ohmmeter mode, check resistance between signal circuit (Dark
    Green/Red wire on XJ and YJ bodies or Red/White wire on ZJ body) and
    ground circuit (Black/Light Blue wire) on MAP sensor connector. If
    resistance is less than 5 ohms, repair short to ground in Dark
    Green/Red wire on XJ and YJ bodies or Red/White wire on ZJ body.
    Perform TEST VER-1. If resistance is more than 5 ohms, replace PCM.
    Perform TEST VER-1.

TEST FC-6A - MAP SENSOR VOLTAGE TOO HIGH

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

1) Start engine. Using DRB-II, read Manifold Absolute

Pressure (MAP) sensor voltage. If MAP sensor voltage is more than 4.6 volts, go to step 4). If MAP sensor voltage is less than 4.6 volts, wiggle MAP sensor connector and wiring harness while watching DRB-II display. If MAP sensor voltage changes, repair connector or wiring harness as necessary. Perform TEST VER-1.

2) If MAP sensor voltage does not change, condition required
to set fault is not present at this time. MAP SENSOR VOLTAGE TOO HIGH
fault sets if MAP sensor output is more than 4.6 volts at start or
with engine running. Engine speed must be more than 400 RPM but less
than 1500 RPM, and Throttle Position Sensor (TPS) voltage must be less
than one volt. Possible causes are: open MAP sensor signal

circuit(Dark Green/Red wire on XJ and YJ bodies or Red/White wire on ZJ body), MAP sensor open internally, open MAP sensor ground circuit (Black/Light Blue wire) or short to voltage in MAP sensor signal circuit (Dark Green/Red wire on XJ and YJ bodies or Red/White wire on ZJ body). Go to next step.

70. Inspect all related wiring and connectors and repair as
    necessary. Perform TEST VER-1. If no problems were found with wiring
    and connectors, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

71. Turn ignition on. Ensure engine is off. Disconnect MAP
    sensor connector. Connect a jumper wire between signal circuit(Dark
    Green/Red wire on XJ and YJ bodies or Red/White wire on ZJ body) and
    ground circuit (Black/Light Blue wire) on MAP sensor connector. Using
    DRB-II, read MAP sensor voltage. If voltage is less than one volt,

replace MAP sensor. Perform TEST VER-1.

72. If MAP sensor voltage is more than one volt, move jumper
    wire from MAP sensor connector, ground circuit (Black/Light Blue wire)
    to an engine ground. Using DRB-II, read MAP sensor voltage.

73. If MAP sensor voltage is less than one volt, repair open
    in Black/Light Blue wire. Perform TEST VER-1. If MAP sensor voltage is
    more than one volt, turn ignition off. Disconnect Powertrain Control
    Module (PCM) connector.

74. Using an external ohmmeter, check resistance of signal
    circuit (Dark Green/Red wire on XJ and YJ bodies or Red/White wire on
    ZJ body) between MAP sensor connector and PCM connector terminal No.
    1. If resistance is less than 5 ohms, replace PCM. Perform TEST VER-1.
    If resistance is more than 5 ohms, repair open in Dark Green/Red wire
    on XJ and YJ bodies or Red/White wire on ZJ body. Perform TEST VER-1.

TEST FC-7A - NO VEHICLE SPEED SENSOR SIGNAL

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

75. Raise vehicle so drive wheels are free to spin. Start
    engine. Using DRB-II, read Vehicle Speed Sensor (VSS) signal. Put
    transmission in any forward gear. If DRB-II displays more than zero
    MPH, go to next step. If DRB-II does not display more than zero MPH,
    go to step 4).

76. Condition required to set fault is not present at this
    time. NO VEHICLE SPEED SENSOR SIGNAL fault sets if Powertrain Control
    Module (PCM) does not see a VSS signal at PCM terminal No. 47

(White/Orange wire) under road load conditions. Possible causes are: open or shorted VSS signal circuit (White/Orange wire), open VSS sensor 8-volt supply circuit (Orange wire on XJ and YJ bodies or White/Black wire on ZJ body), open VSS sensor ground circuit

(Black/Light Blue wire), failed VSS sensor, failed Daytime Running Light (DRL) module (if equipped) or failed Powertrain Control Module

(PCM). Go to next step.

77. Inspect all related wiring and connectors and repair as
    necessary. Perform TEST VER-1. If no problems were found with wiring
    and connectors, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

78. Turn ignition off. Disconnect Vehicle Speed Sensor (VSS)
    connector. Turn ignition on. Using DRB-II in voltmeter mode, check
    voltage on VSS sensor connector, 8-volt supply circuit (Orange wire on
    XJ and YJ bodies or White/Black wire on ZJ body). If voltage is more
    than 7 volts, go to next step. If voltage is less than 7 volts, repair
    open in Orange wire on XJ and YJ bodies or White/Black wire on ZJ
    body. Perform TEST VER-1.

79. Using DRB-II, check voltage on VSS sensor connector,
    signal circuit (White/Orange wire). If voltage is less than 4 volts,
    go to TEST FC-7B. If voltage is more than 4 volts, turn ignition off.
    Connect a jumper wire between VSS signal circuit (White/Orange wire)
    and ground circuit (Black/Light Blue wire) on VSS sensor connector.

80. Turn ignition on. Using DRB-II, read vehicle speed. Make
    and break connection at VSS sensor connector several times while
    observing DRB-II display. If DRB-II displays vehicle speed as more
    than zero MPH, replace VSS. Perform TEST VER-1. If DRB-II does not
    display more than zero MPH, turn ignition off. Using DRB-II in
    ohmmeter mode, check resistance on VSS sensor connector, ground
    circuit (Black/Light Blue wire). If resistance is less than 5 ohms, go
    to next step. If resistance is more than 5 ohms, repair open in
    Black/Light Blue wire. Perform TEST VER-1.

7) Turn ignition off. Disconnect Powertrain Control Module
(PCM) connector. Using an external ohmmeter, check resistance of

signal circuit (White/Orange wire) between VSS connector harness side and PCM connector terminal No. 47. If resistance is more than 5 ohms, repair open in White/Orange wire. Perform TEST VER-1. If resistance is less than 5 ohms, replace PCM. Perform TEST VER-1.

TEST FC-7B - NO VEHICLE SPEED SENSOR SIGNAL

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

1) Turn ignition off. Disconnect Powertrain Control Module
(PCM) connector. Inspect PCM connector for damaged or pushed-out

terminals. Repair as necessary. Perform TEST VER-1. If no problems were found with wiring or connectors, go to next step.

81. Using DRB-II in ohmmeter mode, check resistance of PCM
    connector terminal No. 47 (White/Orange wire). If resistance is more
    than 5 ohms, go to step 4). If resistance is less than 5 ohms,
    disconnect Daytime Running Lights (DRL) module connector (if
    equipped). If vehicle is not equipped with DRL, repair short to ground
    in White/Orange wire. DRL module is located near blower motor on XJ
    body, near coolant overflow reservoir on YJ body or under Power
    Distribution Center on ZJ body. Using DRB-II, check resistance of PCM
    connector terminal No. 47 (White/Orange wire).

82. If resistance is more than 5 ohms, replace DRL module.
    Perform TEST VER-1. If resistance is less than 5 ohms, repair short to
    ground in White/Orange wire. Perform TEST VER-1.

83. Using an external ohmmeter, check resistance of signal
    circuit(White/Orange wire) between VSS sensor connector and PCM
    connector terminal No. 47. If resistance is less than 5 ohms, replace
    PCM. Perform TEST VER-1. If resistance is more than 5 ohms, repair
    open in White/Orange wire. Perform TEST VER-1

TEST FC-8A - OXYGEN (O2) SENSOR STAYS AT CENTER

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

84. Start engine. Allow engine to run until normal operating
    temperature is reached. Using DRB-II, set engine speed to 1500 RPM.
    Using DRB-II, read oxygen sensor state. If oxygen sensor is not
    switching from rich to lean, go to step 4). If oxygen sensor is
    switching from rich to lean, wiggle sensor connector and wiring
    harness while watching DRB-II display.

85. If oxygen sensor was locked at center at any time, inspect
    all related wiring and connectors and repair as necessary. Perform
    TEST VER-1. If oxygen sensor was not locked at center at any time,
    condition required to set fault is not present at this time. O2S STAYS
    AT CENTER fault sets if oxygen sensor output voltage stays at .5 volt
    for 1.5 minutes with engine temperature more than 170F (77C) and
    engine running for 2 minutes. Possible causes are: open oxygen sensor
    circuit or oxygen sensor failure. Go to next step.

86. Inspect all related wiring and connectors and repair as
    necessary. Perform TEST VER-1. If no problems were found with wiring
    and connectors, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

87. Turn ignition off. Disconnect oxygen sensor connector.
    Using DRB-II in ohmmeter mode, check resistance of ground circuit

(Black/Light Blue wire) at oxygen sensor connector harness side. If resistance is more than 5 ohms, repair open in Black/Light Blue wire. Perform TEST VER-1.

88. If resistance is less than 5 ohms, connect a jumper wire
    between oxygen sensor signal circuit (Black/Dark Green wire on XJ and
    YJ bodies or Black/Orange wire on ZJ body) and battery positive
    terminal. Using DRB-II, read oxygen sensor voltage. If oxygen sensor
    voltage is more than one volt, replace oxygen sensor. Perform TEST
    VER-1.

89. If oxygen sensor voltage is less than one volt, turn
    ignition off. Disconnect Powertrain Control Module (PCM) connector.
    Disconnect jumper wire between oxygen sensor signal circuit

(Black/Dark Green wire on XJ and YJ bodies or Black/Orange wire on ZJ body) and battery positive terminal.

7) Using an external ohmmeter, check resistance of signal
circuit(Black/Dark Green wire on XJ and YJ bodies or Black/Orange wire
on ZJ body) between oxygen sensor connector harness side and PCM
connector terminal No. 41. If resistance is less than 5 ohms, replace
PCM. Perform TEST VER-1. If resistance is more than 5 ohms, repair
open in Black/Dark Green wire on XJ and YJ bodies or Black/Orange wire
on ZJ body. Perform TEST VER-1.

TEST FC-9A - OXYGEN (O2) SENSOR SHORTED TO VOLTAGE

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

90. Using DRB-II, read oxygen sensor voltage. If oxygen sensor
    voltage is more than 1.2 volts, go to step 4). If oxygen sensor
    voltage is less than 1.2 volts, wiggle oxygen sensor connector and
    wiring harness while watching DRB-II display. If voltage goes to more
    than 1.2 volts at any time, repair wiring and connectors as necessary.
    Perform TEST VER-1.

91. If voltage does not go to more than 1.2 volts at any time,
    condition required to set fault is not present at this time. O2S
    SHORTED TO VOLTAGE fault sets if oxygen sensor signal circuit voltage
    goes to more than 1.2 volts. Possible causes are: oxygen sensor signal
    circuit (Black/Dark Green wire on XJ and YJ bodies or Black/Orange
    wire on ZJ body) shorted to another circuit, oxygen sensor connector
    has excessive dirt, grease and/or water build-up, or oxygen sensor
    failure. Go to next step.

92. Inspect all related wiring and connectors and repair as
    necessary. Perform TEST VER-1. If no problems were found with wiring
    and connectors, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

93. Turn ignition off. Disconnect oxygen sensor connector.
    Using DRB-II in voltmeter mode, read oxygen sensor voltage. If voltage
    is more than 1.2 volts, repair short to voltage in Black/Dark Green
    wire on XJ and YJ bodies or Black/Orange wire on ZJ body, on oxygen
    sensor connector harness side. Perform TEST VER-1. If voltage is less
    than 1.2 volts, replace oxygen sensor. Perform TEST VER-1.

TEST FC-10A - OXYGEN (O2) SENSOR STAYS ABOVE CENTER (RICH)

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

1) Start engine. Allow engine to run until normal operating temperature is reached. Using DRB-II, set engine speed to 1500 RPM. Using DRB-II, read oxygen sensor voltage. If oxygen sensor voltage is not always more than .5 volt, condition required to set fault is not present at this time. Go to next step. If oxygen sensor voltage is always more than .5 volt, go to step 3).

94. O2S STAYS ABOVE CENTER (RICH) fault sets if oxygen sensor
    output voltage stays at more than .5 volt, but less than 1.2 volts,
    without changing for more than 8 minutes. Possible causes are: high
    fuel pressure, other engine sensor calibration failures, ignition
    system failure, oxygen sensor failure or fuel contamination. Go to
    TEST NF-1A.

95. Using DRB-II, stop all actuation tests. Turn ignition off.
    Inspect air cleaner filter and inlet ducts for restrictions. If
    restrictions are present, repair as necessary. Perform TEST VER-1. If
    restrictions are not present, remove fuel injector rail assembly.

96. Turn ignition on. Using DRB-II, actuate ASD fuel system
    test. Inspect all injectors for leakage. If injectors are leaking,
    stop ASD fuel system test. Replace leaking fuel injectors as
    necessary. Perform TEST VER-1.

97. If injectors are not leaking, using DRB-II, stop ASD fuel
    system test. A condition causing engine to run rich is present. Return
    to step 2).

TEST FC-11A - OXYGEN (O2) SENSOR STAYS BELOW CENTER (LEAN)

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

98. Start engine. Allow engine to run until normal operating
    temperature is reached. Using DRB-II, set engine speed to 1500 RPM.
    Using DRB-II, read oxygen sensor voltage. If oxygen sensor voltage is
    not always less than .5 volt, condition required to set fault is not
    present at this time. Go to next step. If oxygen sensor voltage is
    always less than .5 volt, go to step 3).

99. O2S STAYS BELOW CENTER (LEAN) fault sets if oxygen sensor
    output voltage stays at less than .5 volt without changing for more
    than 8 minutes. Possible causes are: large vacuum leak, low fuel
    pressure, other engine sensor calibration failures, ignition system
    failure, oxygen sensor failure or fuel contamination. Go to TEST NF-
    1A.

100. Using DRB-II, check if oxygen sensor voltage is always
     zero volts. If oxygen sensor voltage is always zero volts, go to next
     step. If oxygen sensor voltage is not always zero volts, a condition
     causing engine to run lean is present. Go to TEST NF-1A.

101. Using DRB-II, stop all actuation tests. Turn ignition on
     with engine off. Disconnect oxygen sensor connector. Using DRB-II,
     read oxygen sensor state. If oxygen sensor state is at center, replace
     oxygen sensor. Perform TEST VER-1.

102. If oxygen sensor state is not at center, turn ignition
     off. Disconnect Powertrain Control Module (PCM) connector. Using DRB-
     II in ohmmeter mode, check resistance of oxygen sensor connector
     (harness side), signal circuit (Black/Dark Green wire on XJ and YJ

bodies or Black/Orange wire on ZJ body).

6) If resistance is less than 5 ohms, repair short to ground
in Black/Dark Green wire on XJ and YJ bodies or Black/Orange wire on
ZJ body. Perform TEST VER-1. If resistance is more than 5 ohms,
replace PCM. Perform TEST VER-1.

TEST FC-12A - ECT SENSOR VOLTAGE TOO HIGH

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

1) Using DRB-II, read Engine Coolant Temperature (ECT) sensor

voltage. If voltage is more than 4.5 volts, go to step 4). If voltage is less than 4.5 volts, while observing DRB-II, wiggle wiring harness from ECT sensor to Powertrain Control Module (PCM). If voltage changes, repair wiring harness as necessary. Perform TEST VER-1.

2) If voltage does not change, condition required to set
fault is not present at this time. ECT SENSOR VOLTAGE TOO HIGH fault
sets if ECT sensor signal circuit (Tan/Black wire) is more than 4.9
volts. Possible causes are: open ECT sensor signal circuit (Tan/Black
wire), ECT sensor open internally or open ECT sensor ground circuit

(Black/Light Blue wire). Go to next step.

103. Inspect all related wiring and connectors and repair as
     necessary. Perform TEST VER-1. If no problems were found with wiring
     and connectors, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

104. Disconnect ECT sensor connector. Connect a jumper wire
     between signal circuit (Tan/Black wire) and ground circuit

(Black/Light Blue wire) on ECT sensor connector. Using DRB-II, read ЕСТ sensor voltage.

105. If voltage is less than one volt, replace ECT sensor.
     Perform TEST VER-1. If voltage is more than one volt, move jumper wire
     from ECT sensor connector, ground circuit (Black/Light Blue wire) to
     an engine ground.

106. Using DRB-II, read ECT sensor voltage. If voltage is less
     than one volt, repair open in Black/Light Blue wire. Perform TEST VER-
     1. If voltage is more than one volt, turn ignition off. Disconnect
     Powertrain Control Module (PCM) connector.

107. Using an external ohmmeter, check resistance of signal
     circuit(Tan/Black wire) between ECT sensor connector and PCM connector
     terminal No. 2. If resistance is more than 5 ohms, repair open in
     Tan/Black wire. Perform TEST VER-1. If resistance is less than 5 ohms,
     replace PCM. Perform TEST VER-1.

TEST FC-13A - ECT SENSOR VOLTAGE TOO LOW

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

108. Using DRB-II, read Engine Coolant Temperature (ECT) sensor
     voltage. If voltage is less than .5 volt, go to step 4). If voltage is
     more than .5 volt, wiggle wiring harness from ECT sensor to Powertrain
     Control Module (PCM) while observing DRB-II. If voltage changes,
     repair wiring harness as necessary. Perform TEST VER-1.

109. If voltage does not change, condition required to set
     fault is not present at this time. ECT SENSOR VOLTAGE TOO LOW fault
     sets if ECT sensor signal circuit (Tan/Black wire) is less than .5
     volt. Possible causes are: short to ground in ECT sensor signal
     circuit (Tan/Black wire) or ECT sensor shorted internally. Go to next
     step.

110. Inspect all related wiring and connectors and repair as
     necessary. Perform TEST VER-1. If no problems were found with wiring
     and connectors, see INACTIVE FAULT CONDITION. Perform TEST VER-2.

111. Disconnect ECT sensor connector. Using DRB-II, read ECT
     sensor voltage. If voltage is more than 4 volts, replace ECT sensor.
     Perform TEST VER-1. If voltage is less than 4 volts, turn ignition
     off. Disconnect PCM connector.

112. Put DRB-II in ohmmeter mode. Using DRB-II, check

resistance of ECT sensor connector, signal circuit (Tan/Black wire). If resistance is more than 5 ohms, replace PCM. Perform TEST VER-1. If resistance is less than 5 ohms, repair short to ground in Tan/Black wire. Perform TEST VER-1.

TEST FC-14A - INTAKE AIR TEMP SENSOR VOLTAGE LOW

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

113. Using DRB-II, read Intake Air Temperature Sensor (IAT)
     voltage. If IAT voltage is less than .5 volt, go to step 4). If IAT
     voltage is more than .5 volt, wiggle wiring harness from IAT sensor to
     Powertrain Control Module (PCM) while observing DRB-II. If voltage
     changed, repair wiring harness as necessary.

114. If voltage does not change, condition required to set
     fault is not present at this time. INTAKE AIR TEMP SENSOR VOLTAGE LOW
     fault sets if IAT signal circuit (Black/Red wire), is less than .5
     volt. Possible causes are: short to ground in IAT signal circuit

(Black/Red wire) or IAT sensor shorted internally. Go to next step.

115. Inspect all related wiring and connectors and repair as
     necessary. Perform TEST VER-1. If no problems were found with wiring
     and connectors, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

116. Disconnect IAT sensor connector. Using DRB-II, read IAT
     sensor voltage. If voltage is more than 4 volts, replace IAT sensor.
     Perform TEST VER-1. If voltage is less than 4 volts, turn ignition
     off. Disconnect PCM connector.

117. Using DRB-II in ohmmeter mode, check resistance of IAT
     sensor connector, signal circuit (Black/Red wire). If resistance is
     less than 5 ohms, repair short to ground in Black/Red wire. Perform
     TEST VER-1. If resistance is more than 5 ohms, replace PCM. Perform
     TEST VER-1.

TEST FC-15A - INTAKE AIR TEMP SENSOR VOLTAGE HIGH

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

118. Using DRB-II, read Intake Air Temperature Sensor (IAT)
     voltage. If IAT voltage is more than 4.5 volts, go to step 4). If IAT
     voltage is less than 4.5 volts, while observing DRB-II display, wiggle
     wiring harness from IAT sensor to Powertrain Control Module (PCM). If
     voltage changed, repair wiring harness as necessary.

119. If voltage does not change, condition required to set
     fault is not present at this time. INTAKE AIR TEMP SENSOR VOLTAGE HIGH
     fault sets if IAT signal circuit (Black/Red wire), is more than 4.9
     volts. Possible causes are: open IAT signal circuit (Black/Red wire),
     IAT sensor open internally or open IAT sensor ground circuit
     (Black/Light Blue wire). Go to next step.

120. Inspect all related wiring and connectors and repair as
     necessary. Perform TEST VER-1. If no problems were found with wiring
     and connectors, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

121. Disconnect IAT sensor connector. Connect jumper wire
     between signal circuit (Black/Red wire) and ground circuit

(Black/Light Blue wire) on IAT sensor connector. Using DRB-II, read IAT sensor voltage. If voltage is less than one volt, replace IAT sensor. Perform TEST VER-1.

122. If voltage is more than one volt, move jumper wire from
     IAT sensor connector, ground circuit (Black/Light Blue wire) to an
     engine ground. Using DRB-II, read IAT sensor voltage. If voltage is
     less than one volt, repair open in Black/Light Blue wire. If voltage
     is more than one volt, turn ignition off. Disconnect PCM connector.

123. Using an external ohmmeter, check resistance of signal
     circuit(Black/Red wire) between IAT sensor connector and PCM connector
     terminal No. 21. If resistance is more than 5 ohms, repair open in

Black/Red wire. Perform TEST VER-1. If resistance is less than 5 ohms, replace PCM. Perform TEST VER-1.

TEST FC-16A - THROTTLE POSITION SENSOR VOLTAGE HIGH

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

124. Using DRB-II, read Throttle Position Sensor (TPS) voltage.
     If TPS voltage is more than 4.5 volts, go to step 5). If TPS voltage
     is less than 4.5 volts, while observing DRB-II, slowly open and close
     throttle.

125. If voltage change is not smooth, replace TPS. Perform TEST
     VER-1. If voltage change is smooth, while observing DRB-II, wiggle
     wiring harness from TPS to Powertrain Control Module (PCM). If voltage
     changes, repair wiring harness as necessary. Perform TEST VER-1.

126. If voltage does not change, condition required to set
     fault is not present at this time. THROTTLE POSITION SENSOR VOLTAGE
     HIGH fault sets if TPS signal circuit (Orange/Dark Blue wire) is more
     than 4.5 volts. Possible causes are: open TPS signal circuit

(Orange/Dark Blue wire), open TPS ground circuit (Black/Light Blue wire) or TPS sensor failure. Go to next step.

127. Inspect all related wiring and connectors and repair as
     necessary. Perform TEST VER-1. If no problems were found with wiring
     and connectors, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

128. Disconnect TPS connector. Connect a jumper wire between
     TPS signal circuit (Orange/Dark Blue wire) and TPS ground circuit
     (Black/Light Blue wire) on TPS connector. Using DRB-II, read TPS

voltage. If voltage is less than one volt, replace TPS. Perform TEST VER-1.

129. If voltage is more than one volt, move jumper wire from
     TPS connector, ground circuit (Black/Light Blue wire), to an engine
     ground. Using DRB-II, read TPS sensor voltage.

130. If TPS sensor voltage is less than one volt, repair open
     in Black/Light Blue wire. Perform TEST VER-1. If TPS voltage is more
     than one volt, turn ignition off. Disconnect Powertrain Control Module

(PCM) connector.

8) Using an external ohmmeter, check resistance of TPS signal
circuit (Orange/Dark Blue wire) between TPS connector and PCM
connector terminal No. 22. If resistance is less than 5 ohms, replace
PCM. Perform TEST VER-1. If resistance is more than 5 ohms, repair
open in Orange/Dark Blue wire. Perform TEST VER-1.

TEST FC-17A - THROTTLE POSITION SENSOR VOLTAGE LOW

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

131. Using DRB-II, read Throttle Position Sensor (TPS) voltage.
     If TPS voltage is less than .2 volt, go to step 5). If TPS voltage is
     more than .2 volt, while observing DRB-II, slowly open and close
     throttle.

132. If voltage change is not smooth, replace TPS. Perform TEST
     VER-1. If voltage change is smooth, while observing DRB-II, wiggle
     wiring harness from TPS to Powertrain Control Module (PCM). If voltage
     changes, repair wiring harness as necessary. Perform TEST VER-1.

133. If voltage does not change, condition required to set
     fault is not present at this time. THROTTLE POSITION SENSOR VOLTAGE
     LOW fault sets if TPS signal circuit (Orange/Dark Blue wire) is less

than .2 volt or if vehicle speed is more than 20 MPH, engine speed is more than 1500 RPM and vacuum is less than 2 in. Hg with TPS signal circuit (Orange/Dark Blue wire) less than .5 volt. Possible causes are: short to ground in TPS signal circuit (Orange/Dark Blue wire), TPS sensor failure or open TPS 5-volt supply circuit (Violet/White wire). Go to next step.

134. Inspect all related wiring and connectors and repair as
     necessary. Perform TEST VER-1. If no problems were found with wiring
     and connectors, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

135. Disconnect TPS connector. Using DRB-II, read TPS voltage.
     If voltage is more than one volt, replace TPS. Perform TEST VER-1. If
     voltage is less than one volt, turn ignition off. Disconnect
     Powertrain Control Module (PCM) connector. Using DRB-II in ohmmeter
     mode, check resistance of TPS connector, signal circuit (Orange/Dark
     Blue wire).

136. If resistance is more than 5 ohms, replace PCM. Perform
     TEST VER-1. If resistance is less than 5 ohms, disconnect Transmission
     Control Module (TCM) connector (if equipped). If vehicle is not
     equipped with TCM, repair short to ground in Orange/Dark Blue wire.
     Perform TEST VER-1. On vehicles with TCM, using DRB-II, check
     resistance of TPS connector, signal circuit (Orange/Dark Blue wire).

137. If resistance is less than 5 ohms, repair short to ground
     in Orange/Dark Blue wire. Perform TEST VER-1. If resistance is more
     than 5 ohms, replace TCM. Perform TEST VER-1.

TEST FC-18A - IDLE AIR CONTROL MOTOR CIRCUITS

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

138. Using DRB-II, erase fault messages. Turn ignition off.
     Start engine. Allow engine to reach normal operating temperature.
     Using DRB-II, read fault messages. If DRB-II displays IDLE AIR CONTROL
     MOTOR CIRCUITS, go to step 4).

139. If DRB-II does not display IDLE AIR CONTROL MOTOR

CIRCUITS, condition required to set fault is not present at this time. IDLE AIR CONTROL MOTOR CIRCUITS fault sets if any of 4 Idle Air Control (IAC) motor wires are shorted to ground or battery voltage. Possible causes are: IAC motor internally shorted or IAC motor wires shorted together. Go to next step.

140. Inspect all related wiring and connectors and repair as
     necessary. Perform TEST VER-1. If no problems were found with wiring
     and connectors, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

141. Turn ignition off. Disconnect Idle Air Control (IAC) motor
     connector. Turn ignition on. Using DRB-II, actuate IAC motor. Using
     DRB-II in voltmeter mode, check voltage on each IAC motor connector
     wire at IAC motor connector. Normal voltage reading will switch from
     less than one volt to more than 10 volts.

142. If voltage is less than one volt on any IAC motor wire,
     repair appropriate wire for short to ground. Perform TEST VER-1. If
     voltage is more than 10 volts on any IAC motor wire, repair
     appropriate wire for short to voltage. Perform TEST VER-1.

143. Turn ignition off. Reconnect IAC motor connector.

Disconnect PCM. Using an external ohmmeter, check resistance between terminals No. 39 and 59 at PCM connector. If resistance is more than 35 ohms, go to next step. If resistance is less than 35 ohms, replace IAC motor. Perform TEST VER-1.

7) Using an external ohmmeter, check resistance between
terminals No. 40 and 60 at PCM connector. If resistance is less than
35 ohms, replace IAC motor. Perform TEST VER-1. If resistance is more
than 35 ohms, check resistance between terminals No. 39 and 60 at PCM

connector using DRB-II.

144. If resistance is more than 10 ohms, but less than 75 ohms,
     go to step 10). If resistance is less than 10 ohms, repair IAC driver
     circuits No. 1 and 2 for shorting together. See appropriate PCM
     TERMINAL IDENTIFICATION table for wire color identification. Perform
     TEST VER-1.

145. If resistance is 75-120 ohms, repair IAC driver circuits
     No. 3 and 4 for shorting together. See appropriate PCM TERMINAL
     IDENTIFICATION table for wire color identification. Perform TEST VER-
     1. If resistance is more than 120 ohms, replace PCM. Perform TEST VER-
     1.

146. If resistance is less than 75 ohms, check resistance
     between terminals No. 59 and 60 at PCM connector. If resistance is
     less than 10 ohms, repair IAC driver circuits No. 2 and 4 for shorting
     together. See appropriate PCM TERMINAL IDENTIFICATION table for wire
     color identification. Perform TEST VER-1.

147. If resistance is more than 10 ohms, repair IAC driver
     circuits No. 1 and 4 for shorting together. See appropriate PCM
     TERMINAL IDENTIFICATION table for wire color identification. Perform
     TEST VER-1.

PCM TERMINAL IDENTIFICATION TABLE (1) (XJ & YJ BODIES)

Wire Color & IAC Connector

(PCM Terminal No.) Driver No. Terminal No.

Gray/Red (39) 3 1

Brown/White (40) 1 3

Violet/Black (59) 4 4

Yellow/Black (60) 2 2

(1) - For connector terminal identification, see CONNECTOR IDENTIFICATION at beginning of article.

PCM TERMINAL IDENTIFICATION TABLE (1) (ZJ BODY)

Wire Color & IAC Connector

(PCM Terminal No.) Driver No. Terminal No.

Yellow/Black (39) 3 1

Brown/White (40) 1 3

Gray/Red (59) 4 4

Violet/Black (60) 2 2

(1) - For connector terminal identification, see CONNECTOR IDENTIFICATION at beginning of article.

TEST FC-19A - INJECTOR #1 CONTROL CIRCUIT

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

148. Using DRB-II, erase fault messages. Attempt to start
     engine. If engine will not start, crank engine for at least 10
     seconds.

149. Using DRB-II, read fault messages. If engine started,
     allow engine to idle for at least 20 seconds. If DRB-II does not
     display INJECTOR #1 CONTROL CIRCUIT, condition required to set fault
     is not present at this time. Go to next step. If DRB-II displays

INJECTOR #1 CONTROL CIRCUIT, go to step 6).

3) INJECTOR #1 CONTROL CIRCUIT fault sets if Powertrain
Control Module (PCM) does not detect injector "turn off edge" when
expected. Possible causes are: open or shorted injector ground circuit

(White/Dark Blue wire), open injector power supply circuit (Dark Green/Orange wire on XJ and YJ bodies or Dark Green/Black wire on ZJ body), open injector, or failed driver in Powertrain Control Module

(PCM). Go to next step.

150. Inspect all related wiring and connectors and repair as
     necessary. Perform TEST VER-1. If no problems were found with wiring
     and connectors, go to next step.

151. Start engine. Wiggle wiring harness from injector No. 1 to
     Powertrain Control Module (PCM). If engine misfires or stalls, repair
     wiring harness as necessary. Perform TEST VER-1. If engine does not
     misfire or stall, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

152. Turn ignition off. Disconnect injector No. 1 connector.
     Using an external ohmmeter, check resistance of injector No. 1. If
     resistance is not 10-16 ohms, replace injector. Perform TEST VER-1. If
     resistance is 10-16 ohms, turn ignition on. Using DRB-II, actuate
     injector No. 1.

153. Using DRB-II in voltmeter mode, check voltage on injector
     connector (harness side) Dark Green/Orange wire on XJ and YJ bodies or
     Dark Green/Black wire on ZJ body. If voltage is less than 10 volts,
     repair open in Dark Green/Orange wire on XJ and YJ bodies or Dark
     Green/Black wire on ZJ body. Perform TEST VER-1.

154. If voltage is more than 10 volts, turn ignition off.
     Disconnect Powertrain Control Module (PCM) connector. Using an
     external ohmmeter, check resistance of injector driver circuit

(White/Dark Blue wire), between PCM connector terminal No. 16 and injector connector. If resistance is less than 5 ohms, go to next step. If resistance is more than 5 ohms, repair open in White/Dark Blue wire. Perform TEST VER-1.

9) Using DRB-II in ohmmeter mode, check resistance of PCM
connector terminal No. 16, injector driver circuit (White/Dark Blue
wire). If resistance is less than 5 ohms, repair short to ground in
White/Dark Blue wire. Perform TEST VER-1. If resistance is more than 5
ohms, replace PCM. Perform TEST VER-1.

TEST FC-20A - INJECTOR #2 CONTROL CIRCUIT

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

155. Using DRB-II, erase fault messages. Attempt to start
     engine. If engine will not start, crank engine for at least 10
     seconds.

156. Using DRB-II, read fault messages. If engine started,
     allow engine to idle for at least 20 seconds. If DRB-II does not
     display INJECTOR #2 CONTROL CIRCUIT, condition required to set fault
     is not present at this time. Go to next step. If DRB-II displays
     INJECTOR #2 CONTROL CIRCUIT, go to step 6).

157. INJECTOR #2 CONTROL CIRCUIT fault sets if Powertrain
     Control Module (PCM) does not detect injector "turn off edge" when
     expected. Possible causes are: open or shorted injector ground circuit

(Tan wire), open injector power supply circuit (Dark Green/Orange wire on XJ and YJ bodies or Dark Green/Black wire on ZJ body), open injector, or failed driver in Powertrain Control Module (PCM). Go to next step.

4) Inspect all related wiring and connectors and repair as
necessary. Perform TEST VER-1. If no problems were found with wiring
and connectors, go to next step.

158. Start engine. Wiggle wiring harness from injector No. 2 to
     Powertrain Control Module (PCM). If engine misfires or stalls, repair
     wiring harness as necessary. Perform TEST VER-1. If engine does not
     misfire or stall, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

159. Turn ignition off. Disconnect injector No. 2 connector.
     Using an external ohmmeter, check resistance of injector No. 2. If
     resistance is not 10-16 ohms, replace injector. Perform TEST VER-1. If
     resistance is 10-16 ohms, turn ignition on. Using DRB-II, actuate
     injector No. 2.

160. Using DRB-II in voltmeter mode, check voltage on injector
     connector (harness side) Dark Green/Orange wire on XJ and YJ bodies or
     Dark Green/Black wire on ZJ body. If voltage is less than 10 volts,
     repair open in Dark Green/Orange wire on XJ and YJ bodies or Dark
     Green/Black wire on ZJ body. Perform TEST VER-1.

161. If voltage is more than 10 volts, turn ignition off.
     Disconnect Powertrain Control Module (PCM) connector. Using an
     external ohmmeter, check resistance of injector driver circuit (Tan
     wire) between PCM connector terminal No. 15 and injector connector. If
     resistance is less than 5 ohms, go to next step. If resistance is more
     than 5 ohms, repair open in Tan wire. Perform TEST VER-1.

162. Using DRB-II in ohmmeter mode, check resistance of PCM
     connector terminal No. 15, injector driver circuit (Tan wire). If
     resistance is less than 5 ohms, repair short to ground in Tan wire.
     Perform TEST VER-1. If resistance is more than 5 ohms, replace PCM.
     Perform TEST VER-1.

TEST FC-21A - INJECTOR #3 CONTROL CIRCUIT

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

163. Using DRB-II, erase fault messages. Attempt to start
     engine. If engine will not start, crank engine for at least 10
     seconds.

164. Using DRB-II, read fault messages. If engine started,
     allow engine to idle for at least 20 seconds. If DRB-II does not
     display INJECTOR #3 CONTROL CIRCUIT, condition required to set fault
     is not present at this time. Go to next step. If DRB-II displays
     INJECTOR #3 CONTROL CIRCUIT, go to step 6).

165. INJECTOR #3 CONTROL CIRCUIT fault sets if Powertrain
     Control Module (PCM) does not detect injector "turn off edge" when
     expected. Possible causes are: open or shorted injector ground
     circuit(Yellow/White wire), open injector power supply circuit (Dark
     Green/Orange wire on XJ and YJ bodies or Dark Green/Black wire on ZJ
     body), open injector, or failed driver in Powertrain Control Module

(PCM). Go to next step.

166. Inspect all related wiring and connectors and repair as
     necessary. Perform TEST VER-1. If no problems were found with wiring
     and connectors, go to next step.

167. Start engine. Wiggle wiring harness from injector No. 3 to
     Powertrain Control Module (PCM). If engine misfires or stalls, repair
     wiring harness as necessary. Perform TEST VER-1. If engine does not
     misfire or stall, see INACTIVE FAULT CONDITION in SELF-DIAGNOSTICS.
     Perform TEST VER-1.

168. Turn ignition off. Disconnect injector No. 3 connector.
     Using an external ohmmeter, check resistance of injector No. 3. If
     resistance is not 10-16 ohms, replace injector. Perform TEST VER-1. If
     resistance is 10-16 ohms, turn ignition on. Using DRB-II, actuate
     injector No. 3.

169. Using DRB-II in voltmeter mode, check voltage on injector
     connector (harness side) Dark Green/Orange wire on XJ and YJ bodies or

Dark Green/Black wire on ZJ body. If voltage is less than 10 volts, repair open in Dark Green/Orange wire on XJ and YJ bodies or Dark Green/Black wire on ZJ body. Perform TEST VER-1.

8) If voltage is more than 10 volts, turn ignition off.
Disconnect Powertrain Control Module (PCM) connector. Using an
external ohmmeter, check resistance of injector driver circuit

(Yellow/White wire) between PCM connector terminal No. 14 and injector connector. If resistance is less than 5 ohms, go to next step. If resistance is more than 5 ohms, repair open in Yellow/White wire. Perform TEST VER-1.

9) Using DRB-II in ohmmeter mode, check resistance of PCM
connector terminal No. 14, injector driver circuit (Yellow/White
wire). If resistance is less than 5 ohms, repair short to ground in
Yellow/White wire. Perform TEST VER-1. If resistance is more than 5
ohms, replace PCM. Perform TEST VER-1.

TEST FC-22A - INJECTOR #4 CONTROL CIRCUIT

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

170. Using DRB-II, erase fault messages. Attempt to start
     engine. If engine will not start, crank engine for at least 10
     seconds.

171. Using DRB-II, read fault messages. If engine started,
     allow engine to idle for at least 20 seconds. If DRB-II does not
     display INJECTOR #4 CONTROL CIRCUIT, condition required to set fault
     is not present at this time. Go to next step. If DRB-II displays
     INJECTOR #4 CONTROL CIRCUIT, go to step 6).

172. INJECTOR #4 CONTROL CIRCUIT fault sets if Powertrain
     Control Module (PCM) does not detect injector "turn off edge" when
     expected. Possible causes are: open or shorted injector ground
     circuit(Light Blue/Brown wire), open injector power supply circuit
     (Dark Green/Orange wire on XJ and YJ bodies or Dark Green/Black wire
     on ZJ body), open injector, or failed driver in Powertrain Control
     Module (PCM). Go to next step.

173. Inspect all related wiring and connectors and repair as
     necessary. Perform TEST VER-1. If no problems were found with wiring
     and connectors, go to next step.

174. Start engine. Wiggle wiring harness from injector No. 4 to
     Powertrain Control Module (PCM). If engine misfires or stalls, repair
     wiring harness as necessary. Perform TEST VER-1. If engine does not
     misfire or stall, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

175. Turn ignition off. Disconnect injector No. 4 connector.
     Using an external ohmmeter, check resistance of injector No. 4. If
     resistance is not 10-16 ohms, replace injector. Perform TEST VER-1. If
     resistance is 10-16 ohms, turn ignition on. Using DRB-II, actuate
     injector No. 4.

176. Using DRB-II in voltmeter mode, check voltage on injector
     connector (harness side) Dark Green/Orange wire on XJ and YJ bodies or
     Dark Green/Black wire on ZJ body. If voltage is less than 10 volts,
     repair open in Dark Green/Orange wire on XJ and YJ bodies or Dark
     Green/Black wire on ZJ body. Perform TEST VER-1.

177. If voltage is more than 10 volts, turn ignition off.
     Disconnect Powertrain Control Module (PCM) connector. Using an
     external ohmmeter, check resistance of injector driver circuit (Light
     Blue/Brown wire), between PCM connector terminal No. 13 and injector
     connector. If resistance is less than 5 ohms, go to next step. If
     resistance is more than 5 ohms, repair open in Light Blue/Brown wire.
     Perform TEST VER-1.

178. Using DRB-II in ohmmeter mode, check resistance of PCM

connector terminal No. 13, injector driver circuit (Light Blue/Brown wire). If resistance is less than 5 ohms, repair short to ground in Light Blue/Brown wire. Perform TEST VER-1. If resistance is more than 5 ohms, replace PCM. Perform TEST VER-1.

TEST FC-23A - INJECTOR #5 CONTROL CIRCUIT

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

179. Using DRB-II, erase fault messages. Attempt to start
     engine. If engine will not start, crank engine for at least 10
     seconds.

180. Using DRB-II, read fault messages. If engine started,
     allow engine to idle for at least 20 seconds. If DRB-II does not
     display INJECTOR #5 CONTROL CIRCUIT, condition required to set fault
     is not present at this time. Go to next step. If DRB-II displays
     INJECTOR #5 CONTROL CIRCUIT, go to step 6).

181. INJECTOR #5 CONTROL CIRCUIT fault sets if Powertrain
     Control Module (PCM) does not detect injector "turn off edge" when
     expected. Possible causes are: open or shorted injector ground circuit

(Pink/Black wire on XJ and YJ bodies or Gray wire on ZJ body), open injector power supply circuit (Dark Green/Orange wire on XJ and YJ bodies or Dark Green/Black wire on ZJ body), open injector, or failed driver in Powertrain Control Module (PCM). Go to next step.

182. Inspect all related wiring and connectors and repair as
     necessary. Perform TEST VER-1. If no problems were found with wiring
     and connectors, go to next step.

183. Start engine. Wiggle wiring harness from injector No. 5 to
     Powertrain Control Module (PCM). If engine misfires or stalls, repair
     wiring harness as necessary. Perform TEST VER-1. If engine does not
     misfire or stall, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

184. Turn ignition off. Disconnect injector No. 5 connector.
     Using an external ohmmeter, check resistance of injector No. 5. If
     resistance is not 10-16 ohms, replace injector. Perform TEST VER-1. If
     resistance is 10-16 ohms, turn ignition on. Using DRB-II, actuate
     injector No. 5.

185. Using DRB-II in voltmeter mode, check voltage on injector
     connector (harness side) Dark Green/Orange wire on XJ and YJ bodies or
     Dark Green/Black wire on ZJ body. If voltage is less than 10 volts,
     repair open in Dark Green/Orange wire on XJ and YJ bodies or Dark
     Green/Black wire on ZJ body. Perform TEST VER-1.

186. If voltage is more than 10 volts, turn ignition off.
     Disconnect Powertrain Control Module (PCM) connector. Using an
     external ohmmeter, check resistance of injector driver circuit

(Pink/Black wire on XJ and YJ bodies or Gray wire on ZJ body) between PCM connector terminal No. 38 and injector connector. If resistance is less than 5 ohms, go to next step. If resistance is more than 5 ohms, repair open in Pink/Black wire on XJ and YJ bodies or Gray wire on ZJ body. Perform TEST VER-1.

9) Using DRB-II in ohmmeter mode, check resistance of PCM
connector terminal No. 38, injector driver circuit (Pink/Black wire on
XJ and YJ bodies or Gray wire on ZJ body). If resistance is less than
5 ohms, repair short to ground in Pink/Black wire on XJ and YJ bodies
or Gray wire on ZJ body. Perform TEST VER-1. If resistance is more
than 5 ohms, replace PCM. Perform TEST VER-1.

TEST FC-24A - INJECTOR #6 CONTROL CIRCUIT

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams,

see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

187. Using DRB-II, erase fault messages. Attempt to start
     engine. If engine will not start, crank engine for at least 10
     seconds.

188. Using DRB-II, read fault messages. If engine started,
     allow engine to idle for at least 20 seconds. If DRB-II does not
     display INJECTOR #6 CONTROL CIRCUIT, condition required to set fault
     is not present at this time. Go to next step. If DRB-II displays
     INJECTOR #6 CONTROL CIRCUIT, go to step 6).

189. INJECTOR #6 CONTROL CIRCUIT fault sets if Powertrain
     Control Module (PCM) does not detect injector "turn off edge" when
     expected. Possible causes are: open or shorted injector ground circuit

(Light Green/Black wire on XJ and YJ bodies or Brown/Yellow wire on ZJ body), open injector power supply circuit (Dark Green/Orange wire on XJ and YJ bodies or Dark Green/Black wire on ZJ body), open injector, or failed driver in Powertrain Control Module (PCM). Go to next step.

190. Inspect all related wiring and connectors and repair as
     necessary. Perform TEST VER-1. If no problems were found with wiring
     and connectors, go to next step.

191. Start engine. Wiggle wiring harness from injector No. 6 to
     Powertrain Control Module (PCM). If engine misfires or stalls, repair
     wiring harness as necessary. Perform TEST VER-1. If engine does not
     misfire or stall, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

192. Turn ignition off. Disconnect injector No. 6 connector.
     Using an external ohmmeter, check resistance of injector No. 6. If
     resistance is not 10-16 ohms, replace injector. Perform TEST VER-1. If
     resistance is 10-16 ohms, turn ignition on. Using DRB-II, actuate
     injector No. 6.

193. Using DRB-II in voltmeter mode, check voltage on injector
     connector (harness side) Dark Green/Orange wire on XJ and YJ bodies or
     Dark Green/Black wire on ZJ body. If voltage is less than 10 volts,
     repair open in Dark Green/Orange wire on XJ and YJ bodies or Dark
     Green/Black wire on ZJ body. Perform TEST VER-1.

194. If voltage is more than 10 volts, turn ignition off.
     Disconnect Powertrain Control Module (PCM) connector. Using an
     external ohmmeter, check resistance of injector driver circuit (Light
     Green/Black wire on XJ and YJ bodies or Brown/Yellow wire on ZJ body),
     between PCM connector terminal No. 58 and injector connector. If
     resistance is less than 5 ohms, go to next step. If resistance is more
     than 5 ohms, repair open in Light Green/Black wire on XJ and YJ bodies
     or Brown/Yellow wire on ZJ body. Perform TEST VER-1.

195. Using DRB-II in ohmmeter mode, check resistance of PCM
     connector terminal No. 58, injector driver circuit (Light Green/Black
     wire on XJ and YJ bodies or Brown/Yellow wire on ZJ body). If
     resistance is less than 5 ohms, repair short to ground in Light
     Green/Black wire on XJ and YJ bodies or Brown/Yellow wire on ZJ body.
     Perform TEST VER-1. If resistance is more than 5 ohms, replace PCM.
     Perform TEST VER-1.

TEST FC-25A - A/C CLUTCH RELAY CIRCUIT

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

1) Using DRB-II, erase fault messages. Turn ignition on. On XJ and YJ bodies, actuate A/C clutch relay using DRB-II. On ZJ body, actuate A/C clutch relay and Auto Shutdown (ASD) relay using DRB-II. On all bodies, if A/C clutch relay is clicking, go to next step. If A/C clutch relay is not clicking, go to step 5).

2) Condition required to set fault is not present at this
time. A/C CLUTCH RELAY CIRCUIT fault sets if A/C clutch relay control
circuit(Dark Blue/Orange wire on XJ and YJ bodies or Dark Blue/Red
wire on ZJ body) is not in its proper state when monitored by
Powertrain Control Module (PCM). Possible causes are: open or short in
A/C clutch relay coil windings, open or short in A/C clutch relay
control circuit (Dark Blue/Orange wire on XJ and YJ bodies or Dark
Blue/Red wire on ZJ body), open or short in A/C clutch relay ignition
feed circuit (Dark Blue/White wire on XJ and YJ bodies or Yellow/Dark
Green wire on ZJ body), or failed driver in Powertrain Control Module

(PCM). Go to next step.

196. Inspect all related wiring and connectors and repair as
     necessary. Perform TEST VER-1. If no problems were found with wiring
     and connectors, go to next step.

197. While still actuating A/C clutch and ASD relay, wiggle
     wiring harness from A/C clutch relay to Powertrain Control Module

(PCM). Stop actuation of relays. Using DRB-II, read fault messages. If A/C CLUTCH RELAY CIRCUIT fault returns, repair wiring harness as necessary. Perform TEST VER-1. If A/C CLUTCH RELAY CIRCUIT fault does not return, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

198. Remove A/C clutch relay. Install a known good A/C clutch
     relay. If known good A/C clutch relay is clicking, replace original
     A/C clutch relay. Perform TEST VER-1. If known good A/C clutch relay
     is not clicking, remove known good A/C clutch relay.

199. Ensure A/C clutch relay actuation test is still running.
     Using DRB-II in voltmeter mode, check voltage on A/C clutch relay
     connector, ignition feed circuit (Dark Blue/White wire on XJ and YJ
     bodies or Yellow/Dark Green wire on ZJ body). If voltage is less than
     10 volts, repair open in Dark Blue/White wire on XJ and YJ bodies or
     Yellow/Dark Green wire on ZJ body. Perform TEST VER-1.

200. If voltage is more than 10 volts, turn ignition off.
     Disconnect Powertrain Control Module (PCM) connector. Using DRB-II in
     ohmmeter mode, check resistance of A/C clutch relay connector, control
     circuit (Dark Blue/Orange wire on XJ and YJ bodies or Dark Blue/Red
     wire on ZJ body). If resistance is less than 5 ohms, repair short to
     ground in Dark Blue/Orange wire on XJ and YJ bodies or Dark Blue/Red
     wire on ZJ body. Perform TEST VER-1.

201. If resistance is more than 5 ohms, check resistance of
     control circuit (Dark Blue/Orange wire on XJ and YJ bodies or Dark
     Blue/Red wire on ZJ body) between A/C clutch relay connector and PCM
     connector terminal No. 34 using an external ohmmeter. If resistance is
     more than 5 ohms, repair open in Dark Blue/Orange wire on XJ and YJ
     bodies or Dark Blue/Red wire on ZJ body. Perform TEST VER-1. If
     resistance is less than 5 ohms, replace PCM. Perform TEST VER-1.

TEST FC-26A - RAD FAN CONTROL RELAY CIRCUIT

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

202. Using DRB-II, erase fault messages. Turn ignition on.
     Using DRB-II, actuate radiator fan relay. If radiator fan relay is
     clicking, condition required to set fault is not present at this time.
     Go to next step. If radiator fan relay is not clicking, go to step 5).

203. RAD FAN CONTROL RELAY CIRCUIT fault sets if radiator fan
     relay control circuit (Dark Blue/Pink wire) is not in its proper state
     when monitored by Powertrain Control Module (PCM). Possible causes
     are: open or short in radiator fan relay coil windings, open or short
     in radiator fan relay control circuit (Dark Blue/Pink wire), open or
     short in radiator fan relay ignition feed circuit (Dark Blue/White
     wire), or failed driver in Powertrain Control Module (PCM). Go to next

step.

204. Inspect all related wiring and connectors and repair as
     necessary. Perform TEST VER-1. If no problems were found with wiring
     and connectors, go to next step.

205. While still actuating radiator fan relay, wiggle wiring
     harness from radiator fan relay to Powertrain Control Module (PCM).
     Stop actuation of radiator fan relay. Using DRB-II, read fault
     messages. If RAD FAN CONTROL RELAY CIRCUIT fault returns, repair
     wiring harness as necessary. Perform TEST VER-1. If RAD FAN CONTROL
     RELAY CIRCUIT fault does not return, see INACTIVE FAULT CONDITION.
     Perform TEST VER-1.

206. Remove radiator fan relay. Install a known good radiator
     fan relay. If known good radiator fan relay is clicking, replace
     original radiator fan relay. Perform TEST VER-1. If known good
     radiator fan relay is not clicking, remove known good radiator fan
     relay.

207. DRB-II should still be actuating radiator fan relay. Using
     DRB-II in voltmeter mode, check voltage on radiator fan relay
     connector, ignition feed circuit (Dark Blue/White wire). If voltage is
     less than 10 volts, repair open in Dark Blue/White wire. Perform TEST
     VER-1. If voltage is more than 10 volts, turn ignition off.

208. Disconnect PCM connector. Using DRB-II in ohmmeter mode,
     check resistance of radiator fan relay connector, control circuit
     (Dark Blue/Pink wire). If resistance is less than 5 ohms, repair short

to ground in Dark Blue/Pink wire. Perform TEST VER-1.

8) If resistance is more than 5 ohms, check resistance of
control circuit (Dark Blue/Pink wire) between radiator fan relay
connector and PCM connector terminal No. 31 using an external
ohmmeter. If resistance is more than 5 ohms, repair open in Dark
Blue/Pink wire. Perform TEST VER-1. If resistance is less than 5 ohms,
replace PCM. Perform TEST VER-1.

TEST FC-27A - AUTO SHUTDOWN RELAY CONTROL CIRCUIT

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

1) Using DRB-II, erase fault messages and actuate Auto

Shutdown (ASD) relay. If ASD relay is clicking, condition required to set fault is not present at this time. Go to next step. If ASD relay is not clicking, go to step 5).

209. AUTO SHUTDOWN RELAY CONTROL CIRCUIT fault sets if Auto
     Shutdown (ASD) relay and fuel pump relay control circuit (Dark
     Blue/Yellow wire on XJ and YJ bodies or Pink wire on ZJ body) are not
     in proper state when monitored by Powertrain Control Module (PCM)
     during cranking. Possible causes are: open or short in ASD relay and
     fuel pump relay control circuits (Dark Blue/Yellow wire on XJ and YJ
     bodies or Pink wire on ZJ body), open or short in ASD relay ignition
     feed circuit (Dark Blue wire on XJ body, White/Yellow wire on YJ body
     or Light Blue/Red wire on ZJ body), or failed driver in Powertrain
     Control Module (PCM). Go to next step.

210. Inspect all related wiring and connectors and repair as
     necessary. Perform TEST VER-1. If no problems were found with wiring
     and connectors, go to next step.

211. While still actuating ASD relay, wiggle wiring harness
     from ASD relay to Powertrain Control Module (PCM). Stop actuation of
     ASD relay. Using DRB-II, read fault messages. If AUTO SHUTDOWN RELAY
     CONTROL CIRCUIT fault returns, repair wiring harness as necessary.
     Perform TEST VER-1. If AUTO SHUTDOWN RELAY CONTROL CIRCUIT fault does
     not return, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

212. Remove ASD relay. Install a known good ASD relay. If known

good ASD relay is clicking, replace original ASD relay. Perform TEST VER-1. If known good ASD relay is not clicking, remove known good ASD relay.

213. DRB-II should still be actuating ASD relay. Using DRB-II
     in voltmeter mode, check voltage on ASD relay connector, ignition feed
     circuit (Dark Blue wire on XJ body, White/Yellow wire on YJ body or
     Light Blue/Red wire on ZJ body). If voltage is less than 10 volts,
     repair open in Dark Blue wire on XJ body, White/Yellow wire on YJ body
     or Light Blue/Red wire on ZJ body. Perform TEST VER-1. If voltage is
     more than 10 volts, turn ignition off.

214. Disconnect PCM connector. Using DRB-II in ohmmeter mode,
     check resistance of ASD relay connector, control circuit (Dark
     Blue/Yellow wire on XJ and YJ bodies or Pink wire on ZJ body). If
     resistance is less than 5 ohms, repair short to ground in Dark
     Blue/Yellow wire on XJ and YJ bodies or Pink wire on ZJ body. Perform
     TEST VER-1.

215. If resistance is more than 5 ohms, check resistance of
     control circuit (Dark Blue/Yellow wire on XJ and YJ bodies or Pink
     wire on ZJ body) between ASD relay connector and PCM connector
     terminal No. 51 using an external ohmmeter. If resistance is more than
     5 ohms, repair open in Dark Blue/Yellow wire on XJ and YJ bodies or
     Pink wire on ZJ body. Perform TEST VER-1. If resistance is less than 5
     ohms, replace PCM. Perform TEST VER-1.

TEST FC-28A - NO ASD RELAY VOLT SENSE AT PCM

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

216. Attempt to start engine. If engine does not start, go to
     step 5). If engine starts, run engine for 5 minutes.

217. Using DRB-II, read fault messages. If DRB-II displays NO
     ASD RELAY VOLT SENSE AT PCM, repair open in Dark Green/Orange wire on
     XJ and YJ bodies or Dark Green/Black wire on ZJ body, between Auto
     Shutdown (ASD) relay connector and Powertrain Control Module (PCM)
     connector terminal No. 57. Perform TEST VER-1.

218. If DRB-II does not display NO ASD RELAY VOLT SENSE AT PCM,
     condition required to set fault is not present at this time. NO ASD
     RELAY VOLT SENSE AT PCM fault sets if ASD output voltage is not sensed
     when ASD relay is energized. Possible causes are: open ASD relay
     output wire (Dark Green/Orange wire on XJ and YJ bodies or Dark
     Green/Black wire on ZJ body), open ASD relay control circuit wire

(Dark Blue/Yellow on XJ and YJ bodies or Pink on ZJ body), failed ASD and fuel pump relays or open battery feed circuit to ASD relay

(Red/Black wire on XJ body, Red/White wire on YJ body or Red wire on ZJ body). Go to next step.

219. Inspect all related wiring and connectors and repair as
     necessary. Perform TEST VER-1. If no problems were found with wiring
     and connectors, see INACTIVE FAULT CONDITION. Perform TEST VER-1. Go
     to next step.

220. If engine does not start, disconnect ASD relay. Using DRB-
     II in voltmeter mode, check voltage on ASD relay connector, battery
     feed circuit (Red/Black wire on XJ body, Red/White wire on YJ body or
     Red wire on ZJ body). If voltage is less than 12 volts, repair open in
     Red/Black wire on XJ body, Red/White wire on YJ body or Red wire on ZJ
     body. Perform TEST VER-1.

221. If voltage is more than 12 volts, turn ignition off.
     Disconnect PCM connector. Using DRB-II in ohmmeter mode, check
     resistance of output circuit (Dark Green/Orange wire on XJ and YJ
     bodies or Dark Green/Black wire on ZJ body) between ASD relay
     connector and PCM connector terminal No. 57.

7) If resistance is more than 5 ohms, repair open in Dark Green/Orange wire on XJ and YJ bodies or Dark Green/Black wire on ZJ body. Perform TEST VER-1. If resistance is less than 5 ohms, reconnect PCM connector. Install a known good ASD relay. Attempt to start engine. If engine starts, replace original ASD relay. Perform TEST VER-1. If engine does not start, replace PCM. Perform TEST VER-1.

TEST FC-29A OR FC-30A - PCM FAILURE SRI MILE NOT STORED

OR PCM FAILURE EEPROM WRITE DENIED

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

1) Turn ignition on. Using DRB-II, perform SRI memory test.
If DRB-II displays WRITE FAILURE, replace Powertrain Control Module
(PCM). Perform TEST VER-1. If DRB-II does not display WRITE FAILURE,

go to next step.

222. If DRB-II displays WRITE REFUSED, go to step 3). If DRB-II
     does not display WRITE REFUSED, go to next step. If DRB-II displays
     SRI MILEAGE INVALID, update mileage and retest SRI memory. Perform
     TEST VER-1. If DRB-II does not display SRI MILEAGE INVALID, compare
     SRI mileage stored with instrument panel odometer. If mileage is same,
     retest SRI memory. Perform TEST VER-1. If mileage is not same, update
     mileage and retest SRI memory. Perform TEST VER-1.

223. When DRB-II displays WRITE REFUSED, Powertrain Control
     Module (PCM) was busy. Using DRB-II, perform SRI memory test. Retest
     SRI memory 2 more times if necessary. If DRB-II displays WRITE
     REFUSED, replace PCM. Perform TEST VER-1. If DRB-II does not display
     WRITE REFUSED, vehicle is functioning properly. Perform TEST VER-1.

TEST FC-31A - FUEL PUMP RESISTOR BY-PASS RELAY CIRCUIT

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

224. Using DRB-II, erase fault messages. Start engine. Using
     DRB-II, read fault messages. If DRB-II displays FUEL PUMP RESISTOR BY­
     PASS RELAY CIRCUIT, go to step 4). If DRB-II does not display FUEL
     PUMP RESISTOR BY-PASS RELAY CIRCUIT, condition required to set fault
     is not present at this time. Go to next step.

225. FUEL PUMP RESISTOR BY-PASS RELAY CIRCUIT fault sets if by­
     pass relay control circuit (Red/Dark Blue wire) is not in its proper
     state when monitored by Powertrain Control Module (PCM). Possible
     causes are: open or shorted relay coil windings, open or shorted relay
     control circuit (Red/Dark Blue wire), open ignition feed circuit(Dark
     Blue/White wire) or failed Powertrain Control Module (PCM). Go to next
     step.

226. Inspect all related wiring and connectors and repair as
     necessary. Perform TEST VER-1. If no problems were found with wiring
     and connectors, see INACTIVE FAULT CONDITION. Perform TEST VER-1.

227. Turn ignition off. Disconnect fuel pump resistor by-pass
     relay connector (located forward of power distribution center,
     underhood). Inspect connector for damaged or pushed-out terminals.
     Repair as necessary. Perform TEST VER-1. If connector is okay, go to
     next step.

228. Using an external ohmmeter, check resistance of by-pass
     relay (Dark Blue/White wire and Red/Dark Blue wire terminals). If
     resistance is more than 80 ohms, replace by-pass relay. Perform TEST
     VER-1. If resistance is less than 80 ohms, turn ignition on.

229. Using DRB-II in voltmeter mode, check voltage of ignition
     feed circuit (Dark Blue/White wire). If voltage is less than 10 volts,
     repair open in Dark Blue/White wire. Perform TEST VER-1. If voltage is
     more than 10 volts, turn ignition off. Disconnect Powertrain Control
     Module (PCM) connector. Go to next step.

230. Using DRB-II in ohmmeter mode, check resistance at PCM
     connector terminal No. 37. If resistance is less than 5 ohms, repair
     short to ground in Red/Dark Blue wire. Perform TEST VER-1. If
     resistance is more than 5 ohms, check resistance between by-pass relay
     connector and PCM connector terminal No. 37 (Red/Dark Blue wire) using
     an external ohmmeter. If resistance is more than 5 ohms, repair open
     in Red/Dark Blue wire. Perform TEST VER-1. If resistance is less than

5 ohms, replace PCM. Perform TEST VER-1.

TEST NF-1A - NO FAULT CODE TEST MENU

No Fault Complete Test

Check MITCHELL(R) TECH SERVICE BULLETINS (TSBs) for any pertinent information. If a TSB exists, perform corrective action. If TSB does not exist or if driveability problem still exists, perform tests NF-2A through NF-12A in sequence until driveability problem is found. See NO FAULT CODE TEST MENU table.

NO FAULT CODE TEST MENU TABLE

Application Test

Checking Secondary Ignition & Timing NF-2A

Checking Fuel Pressure NF-3A

Checking Coolant Sensor Calibration NF-4A

Checking TPS Calibration NF-5A

Checking MAP Sensor Calibration NF-6A

Checking Oxygen (O2) Sensor Switching NF-7A

Checking Idle Air Control Motor NF-8A

Checking Park/Neutral Switch NF-9A

Checking PCM Grounds & Power Circuits NF-10A

Checking Engine Vacuum NF-11A

No Fault Code Mechanical Test NF-12A

No Fault Quick Individual Test

If it is suspected that any item listed in NO FAULT CODE TEST MENU table is cause of a vehicle�s driveability problem, perform associated test(s) individually. Return to NO FAULT CODE TEST MENU table if driveability problem still exists, or perform NO FAULT COMPLETE TEST.

No Fault Quick Symptom Test

Symptom checks cannot be used properly unless driveability problem characteristic actually happens while vehicle is being tested. To reduce diagnostic time, ensure that TEST FC-1A is reviewed before attempting to diagnose a symptom.

Select symptom that most accurately describes vehicle�s driveability problem and then perform test pertaining to this symptom. Perform each test in sequence until problem is found. See NO FAULT QUICK SYMPTOM TEST MENU table.

NO FAULT QUICK SYMPTOM TEST MENU TABLE

Application Test

Hard Start NF-2A, 3A-8A, 10A, НА, 12A

Start & Stall NF-2A, 3A-6A, 8A, 10A, 12A

Hesitation/Sag/Stumble (1)

Surge NF-2A, 3A-8A, 10A, 12A

Lack Of Power/Sluggish NF-2A, 3A-8A, 10A, НА, 12A

Spark Knock/Detonation NF-2A, 3A-7A, НА, 12A

Cuts Out/Misses NF-2A, 3A, 7A, 10A, НА, 12A

Backfire/Popback NF-2A, 3A, 6A, 7A, 10A, НА, 12A

Runs Rough/Unstable/Erratic Idle (1)

Poor Fuel Economy (1)

(1) - Perform tests NF-2A through NF-12A in sequence. See NO FAULT CODE TEST MENU table.

TEST NF-2A - CHECKING SECONDARY IGNITION & TIMING

231. Turn engine off. Connect engine analyzer to engine. Start
     engine and let idle. If engine will not idle, maintain engine speed
     for reading scope pattern. Set scope to read display or parade
     pattern. Follow equipment manufacturer�s procedure for pattern
     analysis.

232. If secondary ignition pattern is not okay, repair

indicated component in secondary ignition system. Perform TEST VER-1. If secondary ignition pattern is okay, disconnect any spark plug wire. Observe secondary kilovolt line.

233. If open circuit secondary voltage is not at least 25
     kilovolts, replace electronic ignition coil. Perform TEST VER-1. If
     open circuit secondary voltage is at least 25 kilovolts, reinstall
     spark plug wire.

234. Ensure engine temperature is more than 180F (82C) before
     proceeding. Using DRB-II, read total spark advance. Increase engine
     speed to 2000 RPM. If spark advance does not change with increase in
     RPM, replace Powertrain Control Module (PCM). Perform TEST VER-1. If
     spark advance changes with increase in RPM, ignition timing is
     functioning properly. Test is complete.

TEST NF-3A - CHECKING FUEL PRESSURE

WARNING: High fuel pressure may be present in fuel lines. Open fuel system with caution. See FUEL PRESSURE RELEASE procedure.

235. Release fuel pressure. Connect fuel pressure gauge to fuel
     rail. Turn ignition on. Using DRB-II, actuate fuel system. If fuel
     pressure is 34-43 psi (2.3-3.0 kg/cm), fuel pressure is normal. Test
     is complete. If fuel pressure is not 34-43 psi (2.3-3.0 kg/cm),
     record fuel pressure reading. If fuel pressure is more than 43 psi (3.
     0 kg/cm), go to TEST NF-3B.

236. If fuel pressure is less than 43 psi (3.0 kg/cm), stop
     fuel system actuation. Turn ignition off. Inspect fuel lines for
     kinked or restricted lines. Repair fuel lines as necessary. Perform
     TEST VER-1.

237. If no kinked or restricted lines exist, release fuel
     pressure. Remove fuel pressure gauge. Install fuel pressure gauge
     between fuel tank and fuel filter. Turn ignition on. Using DRB-II,
     actuate fuel system. If fuel pressure is at least 5 psi (.4 kg/cm)
     more than previously recorded pressure, replace fuel filter. Perform
     TEST VER-1.

CAUTION: DO NOT allow fuel pressure to exceed 60 psi (4.2 kg/cm) when squeezing fuel return hose.

4) If fuel pressure is not at least 5 psi (.4 kg/cm) more
than previous reading, gently squeeze fuel return hose while observing
fuel pressure gauge, ensuring fuel pressure does not exceed 60 psi (4.

2 kg/cm). If fuel pressure increases, replace fuel pressure regulator. Perform TEST VER-1. If fuel pressure does not increase, replace fuel pump and sock assembly. Perform TEST VER-1.

TEST NF-3B - CHECKING FUEL PRESSURE

WARNING: High fuel pressure may be present in fuel lines. Open fuel system with caution. See FUEL PRESSURE RELEASE procedure.

238. Using DRB-II, stop fuel system actuation. Release fuel
     pressure. Ensure fuel tank is at least 1/4 full before performing
     following test. Install fuel pressure gauge and adapter between fuel
     tank and filter at rear of vehicle.

239. Remove fuel return line from fuel pump at fuel tank.
     Connect Fuel Pressure Test Adapter (6541) to fuel return line. Place
     other end of adapter hose into an approved 2-gallon gasoline can. Turn
     ignition on.

240. Using DRB-II, actuate fuel system. Observe fuel pressure
     gauge. If fuel pressure is 34-43 psi (2.3.-3.0 kg/cm), repair fuel
     return line for a restriction at fuel tank. Perform TEST VER-1.

241. If fuel pressure is not 34-43 psi (2.3-3.0 kg/cm), stop
     fuel system actuation. Release fuel pressure. Reconnect fuel return
     line to fuel tank. Disconnect fuel return line from fuel rail.

242. Attach Fuel Pressure Test Adapter (6541) to fuel return
     line nipple at fuel rail. Place other end of adapter hose into an
     approved 2-gallon gasoline can. Turn ignition on. Using DRB-II,
     actuate fuel system. Observe fuel pressure gauge.

243. If fuel pressure is 34-43 psi (2.3-3.0 kg/cm), repair
     fuel return line for a restriction to fuel tank. Perform TEST VER-1.
     If fuel pressure is not 34-43 psi (2.3-3.0 kg/cm), replace fuel
     pressure regulator. Perform TEST VER-1.

TEST NF-4A - CHECKING COOLANT SENSOR CALIBRATION

1) Start engine. Using DRB-II, read Engine Coolant

Temperature (ECT) sensor value. If ECT sensor temperature is more than 180F (82C), stop engine. Allow engine coolant to cool to 150F (66C). Start engine. Allow engine to reach normal operating

temperature of 180F (82C). If ECT sensor value does not increase smoothly, inspect cooling system for mechanical failure. If cooling system is okay, replace ECT sensor. Perform TEST VER-1. If ECT sensor value increases smoothly, go to next step.

2) If ECT sensor value does not reach 180F (82C) or more,
inspect cooling system for mechanical failure. If system is okay,
replace ECT sensor. Perform TEST VER-1. If ECT sensor value reaches
180F (82C) or more, ECT sensor is functioning properly. Test is
complete.

TEST NF-5A - CHECKING TPS CALIBRATION

244. Turn engine off. Turn ignition on. Using DRB-II, read
     Throttle Position Sensor (TPS) voltage. Ensure throttle is fully
     closed and against throttle stop.

245. If voltage is not one volt or less with throttle closed,
     replace TPS. Perform TEST VER-1. If voltage is one volt or less with
     throttle closed, watch voltage while slowly opening throttle wide
     open. If voltage change is not smooth, replace TPS. Perform TEST VER-
     1. If voltage change is smooth, go to next step.

246. If maximum voltage is not at least 3.6 volts at wide open
     throttle, replace TPS. Perform TEST VER-1. If maximum voltage is at
     least 3.6 volts at wide open throttle, using DRB-II in voltmeter mode,
     check minimum throttle voltage. If voltage is not 0 to 1 volt, replace
     TPS. Perform TEST VER-1. If voltage is 0 to 1 volt, TPS is functioning

properly. Test is complete.

TEST NF-6A - CHECKING MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR

CALIBRATION

247. Turn engine off. Install vacuum "T" in MAP sensor vacuum
     hose. Install vacuum gauge. Start engine and let idle. If engine will
     not idle, maintain a constant RPM above idle. Using DRB-II, read MAP
     value. If reading is within one in. Hg of vacuum gauge reading, MAP
     sensor is functioning properly. Test is complete. If reading is not
     within one in. Hg of vacuum gauge reading, turn engine off.

248. Disconnect vacuum gauge. Connect vacuum pump to MAP
     sensor. Apply 5 in. Hg of vacuum to MAP sensor. Turn ignition on.
     Using DRB-II, read and record MAP sensor voltage. Increase vacuum to
     20 in. Hg. Using DRB-II, read and record MAP sensor voltage. Subtract
     20 in. Hg voltage reading from 5 in. Hg voltage reading. If difference
     in voltage is 2.3-2.9 volts, repair restriction in MAP sensor vacuum
     hose. Perform TEST VER-1. If difference in voltage is not 2.3-2.9
     volts, replace MAP sensor. Perform TEST VER-1.

TEST NF-7A - CHECKING OXYGEN (O2) SENSOR SWITCHING

WARNING: High fuel pressure may be present in fuel lines. Open fuel system with caution. See FUEL PRESSURE RELEASE procedure.

249. Allow engine to reach normal operating temperature. Using
     DRB-II, read O2 sensor state. If O2 sensor state is switching, system
     is functioning properly. Test is complete. If O2 sensor state is not
     switching, check if O2 sensor is locked on lean. If O2 sensor is
     locked on lean, go to TEST NF-7B. If O2 sensor is not locked on lean,
     turn engine off.

250. Connect fuel pressure gauge to fuel rail. Turn ignition
     on. Using DRB-II, actuate fuel system. Allow fuel pressure gauge to
     stabilize to normal fuel pressure of 34-43 psi (2.3-3.0 kg/cm) . Stop
     fuel system actuation. Monitor fuel pressure gauge for one minute. Go
     to next step.

251. If gauge pressure decreased more than 10 psi (.8 kg/cm),
     replace leaking fuel injectors or "O" rings as necessary. Perform TEST
     VER-1. If gauge pressure decreased less than 10 psi (.8 kg/cm),
     inspect air cleaner and inlet ducts for restrictions. Repair as
     necessary. Perform TEST VER-1. If no restrictions are observed, go to
     TEST NF-12A.

TEST NF-7B - CHECKING OXYGEN (O2) SENSOR SWITCHING

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

252. Allow engine to idle. Inspect engine for vacuum leaks.
     Repair vacuum leaks as necessary. Perform TEST VER-1. If no vacuum
     leaks exist, read O2 sensor signal voltage using DRB-II.

253. If voltage is more than 0.1 volt, go to step 4). If

voltage is less than 0.1 volt, turn ignition off. Disconnect O2 sensor connector. Disconnect Powertrain Control Module (PCM) connector. Using DRB-II in ohmmeter mode, check resistance of O2 sensor connector

(harness side), signal circuit (Black/Dark Green wire on XJ and YJ bodies or Black/Orange wire on ZJ body).

3) If resistance is less than 10 ohms, repair short to ground
in Black/Dark Green wire on XJ and YJ bodies or Black/Orange wire on
ZJ body. Perform TEST VER-1. If resistance is more than 10 ohms,
replace O2 sensor. Perform TEST VER-1.

254. Turn engine off. Replace O2 sensor. Turn ignition on.
     Using DRB-II, reset adaptive fuel memory. Start engine. Allow engine
     to reach normal operating temperature.

255. Using DRB-II, read O2 sensor state. If O2 sensor state is
     switching, repair is complete. Perform TEST VER-1. If O2 sensor state
     is not switching, go to TEST NF-12A.

TEST NF-8A - CHECKING IDLE AIR CONTROL MOTOR

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

256. Using DRB-II, set engine speed to 1100 RPM. If engine
     speed set at 1050-1150 RPM, idle speed motor is operating properly.
     Test is complete. If engine speed did not set at 1050-1150 RPM, return
     engine to normal idle speed. Disconnect idle air control motor
     connector.

257. Using DRB-II in voltmeter mode, check voltage on idle air
     control motor connector, No. 1 driver circuit (Brown/White wire) while
     momentarily opening and closing throttle. If voltage is less than one
     volt, go to TEST NF-8B. If voltage is more than one volt, go to next
     step.

258. Using DRB-II, check voltage on idle air control motor
     connector,No. 2 driver circuit (Yellow/Black wire on XJ and YJ bodies
     or Violet/Black wire on ZJ body) while momentarily opening and closing
     throttle. If voltage is less than one volt, go to TEST NF-8B. If
     voltage is more than one volt, go to next step.

259. Using DRB-II, check voltage on idle air control motor
     connector,No. 3 driver circuit (Gray/Red wire on XJ and YJ bodies or
     Yellow/Black wire on ZJ body) while momentarily opening and closing
     throttle. If voltage is less than one volt, go to TEST NF-8B. If
     voltage is more than one volt, go to next step.

260. Using DRB-II, check voltage on idle air control motor
     connector,No. 4 driver circuit (Violet/Black wire on XJ and YJ bodies
     or Gray/Red wire on ZJ body) while momentarily opening and closing
     throttle. If voltage is less than one volt, go to TEST NF-8B. If
     voltage is more than one volt, go to next step.

261. Check engine for vacuum leaks. Repair as necessary.

Perform TEST VER-1. If no vacuum leaks are observed, replace idle air control motor. Perform TEST VER-1.

TEST NF-8B - CHECKING IDLE AIR CONTROL MOTOR

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

Turn engine off. Disconnect Powertrain Control Module (PCM) connector. Using an external ohmmeter, check resistance of each wire between Idle Air Control (IAC) motor connector and PCM connector. See appropriate PCM TERMINAL IDENTIFICATION table. If resistance for any wire is more than 10 ohms, repair open on necessary wire. Perform TEST VER-1. If resistance for any wire is less than 10 ohms, replace PCM. Perform TEST VER-1.

PCM TERMINAL IDENTIFICATION TABLE (XJ & YJ BODIES)
Wire Color Terminal No.
Gray/Red 39

Brown/White 40

Violet/Black 59

Yellow/Black 60

PCM TERMINAL IDENTIFICATION TABLE (ZJ BODY)

Wire Color Terminal No.

Yellow/Black 39

Brown/White 40

Gray/Red 59

Violet/Black 60

TEST NF-9A - CHECKING PARK/NEUTRAL SWITCH

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

262. Using DRB-II, read park/neutral switch input state. While
     watching DRB-II display, move gear selector in and out of Park and
     Reverse positions. If display shows P/N and D/R, system is functioning
     properly. Test is complete. If display does not show P/N and D/R, go
     to next step.

263. Turn ignition off. Place gear selector in Park position.
     Disconnect Powertrain Control Module (PCM) connector. Using DRB-II in
     ohmmeter mode, check resistance on PCM connector terminal No. 30,
     park/neutral switch sense circuit (Brown/Yellow wire). Observe DRB-II
     display while moving gear selector in and out of Park and Reverse
     positions.

264. If display switches from less than 5 ohms to more than 5
     ohms, replace PCM. Perform TEST VER-1. If display does not switch from
     less than 5 ohms to more than 5 ohms, check if display always stays
     less than 5 ohms. If display always stays less than 5 ohms, repair
     short to ground in Brown/Yellow wire. Perform TEST VER-1. If display
     does not always stay less than 5 ohms, go to next step.

265. Disconnect park/neutral switch connector. Using an
     external ohmmeter, check resistance of sense circuit (Brown/Yellow
     wire) between park/neutral switch connector and PCM connector terminal
     No. 30. If resistance is less than 10 ohms, replace park/neutral
     switch. Perform TEST VER-1. If resistance is more than 10 ohms, repair
     open in Brown/Yellow wire. Perform TEST VER-1.

TEST NF-10A - CHECKING PCM GROUND & POWER CIRCUITS

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

1) Turn ignition off. Disconnect Powertrain Control Module
(PCM) connector. Using DRB-II in ohmmeter mode, check resistance of

PCM connector terminal No. 5, signal ground circuit (Black/White wire on XJ and YJ bodies or Black/Tan wire on ZJ body). If resistance is more than 5 ohms, repair open in Black/White wire on XJ and YJ bodies or Black/Tan wire on ZJ body. Perform TEST VER-1. If resistance is less than 5 ohms, go to next step.

2) Using DRB-II, check resistance of PCM connector terminal
No. 11, power ground circuit (Black/Tan wire on XJ and ZJ bodies or
Black wire on YJ body). If resistance is more than 5 ohms, repair open

in Black/Tan wire on XJ and ZJ bodies or Black wire on YJ body. Perform TEST VER-1. If resistance is less than 5 ohms, go to next step.

3) Using DRB-II, check resistance of PCM connector terminal No. 12, power ground circuit (Black/Tan wire on XJ and ZJ bodies or Black wire on YJ body). If resistance is more than 5 ohms, repair open in Black/Tan wire on XJ and ZJ bodies or Black wire on YJ body. Perform TEST VER-1. If resistance is less than 5 ohms, reconnect PCM connector. PCM grounds and power circuits are okay.

TEST NF-11A - CHECKING ENGINE VACUUM

Connect a vacuum gauge to engine. Start engine, and let it idle. Normal vacuum reading will vary depending on altitude. Observe vacuum gauge at idle. If vacuum gauge reading is not steady 13-22 in. Hg, perform TEST NF-12A. If vacuum gauge reading is steady 13-22 in. Hg, engine vacuum is normal. Test is complete.

TEST NF-12A - NO FAULT CODE MECHANICAL TEST

NOTE: If coming to this test from O2 sensor test and rich or lean condition is not corrected after checking items listed below, replace Powertrain Control Module (PCM).

At this point in diagnostic test procedure, all engine control systems have been determined to be operating as designed and not causing a driveability problem. Following additional items should be checked as possible causes:

65535. Check if any MITCHELL(R) TECH SERVICE BULLETINS (TSBs) apply
       to vehicle.

65536. Check engine compression.

65537. Check for exhaust system restriction.

65538. Check camshaft and crankshaft sprockets.

65539. Check valve timing.

65540. Check torque converter stall speed.

65541. Check engine vacuum. It must be at least 13 in. Hg in
       Neutral.

65542. Check for fuel contamination.

65543. Ensure PCV system is functioning properly.

65544. Ensure injector control circuit is connected to correct fuel
       injector and injector is not plugged or restricted.

65545. Check power booster for internal vacuum leak.

TEST NS-1A - QUALIFYING NO-START CONDITION

CAUTION: When checking for spark, Powertrain Control Module (PCM)

damage may occur if spark plug cable is held more than 1/4" away from ground.

1) Turn ignition off. Disconnect any spark plug cable at
spark plug. Insert an insulated screwdriver in spark plug cable
terminal. Hold screwdriver within 1/4" of ground.

NOTE: When checking for spark, consider one or 2 sparks as a no-spark condition.

266. While cranking engine for 10 seconds, watch for spark. If
     a good spark occurs, go to TEST NS-2A. If a good spark does not occur,
     reconnect spark plug cable. Disconnect another spark plug cable at
     spark plug, and repeat test.

267. If a good spark occurs, go to TEST NS-2A. If a good spark
     does not occur, turn ignition off. Remove coil cable from distributor

cap. Hold cable within 1/4" of ground. While cranking engine for 10 seconds, watch for spark. If good spark does not occur, go to next step. If good spark occurs, repair distributor cap, rotor or spark plug cables as necessary. Perform TEST VER-1.

268. Turn ignition off. Remove coil cable from coil. Using an
     external ohmmeter, check resistance of coil cable. If resistance is
     more than 15,000 ohms, replace coil cable. If resistance is less than
     15,000 ohms, remove distributor cap. While cranking engine, watch
     distributor rotor. If distributor rotor turns, go to next step. If
     distributor rotor does not turn, repair distributor drive system as
     necessary. Perform TEST VER-1.

269. Install distributor cap and coil cable. Disconnect
     ignition coil connector. Inspect ignition coil connector for damaged
     or pushed-out terminals. Repair as necessary. Perform TEST VER-1. If
     ignition coil connector terminals are okay, go to next step.

270. Turn ignition on. Using DRB-II, actuate ASD fuel system.
     While actuating ASD fuel system, put DRB-II in voltmeter mode. Using
     DRB-II, check voltage on ASD relay connector output circuit(Dark
     Green/Orange wire on XJ and YJ bodies or Dark Green/Black wire on ZJ
     body). If voltage is more than 10 volts, go to next step. If voltage
     is less than 10 volts, repair open in Dark Green/Orange wire on XJ and
     YJ bodies or Dark Green/Black wire on ZJ body. Perform TEST VER-1.

271. Using DRB-II, check voltage on ASD relay connector
     ignition coil driver circuit (Gray wire on XJ and YJ bodies or
     Gray/White wire on ZJ body). If voltage is more than 10 volts, replace
     ignition coil. Perform TEST VER-1. If voltage is less than 10 volts,
     turn ignition off. Go to next step.

272. Disconnect Powertrain Control Module (PCM) connector.
     Using DRB-II in ohmmeter mode, check resistance at terminal No. 19 of
     PCM connector (Gray wire on XJ and YJ bodies or Gray/White wire on ZJ
     body). If resistance is more than 5 ohms, go to next step. If
     resistance is less than 5 ohms, repair short to ground in Gray wire on
     XJ and YJ bodies or Gray/White wire on ZJ body. Perform TEST VER-1.

273. Using an external ohmmeter, check resistance between
     ignition coil connector (Gray wire on XJ and YJ bodies or Gray/White
     wire on ZJ body), and PCM connector terminal No. 19. If resistance is
     more than 5 ohms, repair open in Gray wire on XJ and YJ bodies or
     Gray/White wire on ZJ body. Perform TEST VER-1. If resistance is less
     than 5 ohms, replace PCM. Perform TEST VER-1.

TEST NS-2A - INSPECTING FUEL SYSTEM

WARNING: High fuel pressure may be present in fuel lines. Open fuel system with caution. See FUEL PRESSURE RELEASE procedure.

1) Ensure throttle cables are not holding throttle open. If
throttle is held open, repair as necessary. Perform TEST VER-1. If
throttle is not held open, using DRB-II, read Throttle Position Sensor

(TPS) voltage.

274. If voltage is less than 1.5 volts, go to next step. If
     voltage is more than 1.5 volts, disconnect TPS connector. Inspect
     terminals. Repair as necessary. Perform TEST VER-1. If terminals are
     okay, replace TPS. Perform TEST VER-1.

275. If vehicle is not equipped with a factory vehicle theft
     alarm, go to next step. If vehicle is equipped with factory vehicle
     theft alarm, using DRB-II, read theft alarm status. If DRB-II displays
     FUEL ON, go to next step. If DRB-II does not display FUEL ON, see G -
     BODY TESTS W/ CODES article in the ENGINE PERFORMANCE Section.

276. Using DRB-II, actuate fuel system. Listen for fuel pump
     operation at fuel tank. If fuel pump operation cannot be heard, go to
     TEST NS-5A. If fuel pump operation can be heard, turn ignition off.

277. Ensure fuel tank is at least 1/4 full. Release fuel
     pressure. Install a fuel pressure gauge in fuel supply line. Turn

ignition on. Using DRB-II, actuate fuel system. Read fuel pressure gauge reading.

278. If fuel pressure is more than 43 psi (3.0 kg/cm), go to
     TEST NS-4B. If fuel pressure is not more than 43 psi (3.0 kg/cm), go
     to next step.

279. If pressure is less than 34 psi (2.3 kg/cm), go to TEST
     NS-4A. If pressure is more than 34 psi (2.3 kg/cm), go to next step.

280. If vehicle initially started and stalled repeatedly, go to
     TEST NS-7A. If vehicle did not initially start and stall repeatedly,
     go to TEST NS-3A.

TEST NS-3A - INSPECTING MECHANICAL SYSTEM

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

281. Disconnect Manifold Absolute Pressure (MAP) sensor
     connector. Turn ignition on. Using DRB-II in voltmeter mode, check
     voltage on MAP sensor connector, 5-volt supply circuit (Violet/White
     wire). If voltage is less than 4.5 volts, repair open in Violet/White
     wire. Perform TEST VER-1.

282. If voltage is more than 4.5 volts, reconnect MAP sensor
     connector. Remove all spark plugs. Inspect spark plug tips for wet
     fuel. If spark plug tips are wet, clean and reinstall spark plugs. If
     spark plug tips are not wet, reinstall spark plugs. Turn ignition on.

283. Using DRB-II, read total spark advance while cranking
     engine. If spark advance is not 0-25 degrees BTDC, replace Powertrain
     Control Module (PCM). Perform TEST VER-1.

284. If spark advance is 0-25 degrees BTDC, inspect spark plug
     cables for correct placement. Reposition cables as necessary. Perform
     TEST VER-1. If spark plug cables are okay, turn ignition off. Check
     valve timing. Correct valve timing as necessary. Perform TEST VER-1.

285. If valve timing is okay, check engine compression. Repair
     as necessary. Perform TEST VER-1. If engine compression is okay,
     replace MAP sensor. Perform TEST VER-1.

TEST NS-4A - CORRECTING FUEL DELIVERY

WARNING: High fuel pressure may be present in fuel lines. Open fuel system with caution. See FUEL PRESSURE RELEASE procedure.

286. Record fuel pressure gauge reading. Turn ignition off.
     Release fuel pressure. Remove fuel pressure gauge. Install fuel
     pressure gauge between fuel tank and fuel filter. Turn ignition on.

287. Using DRB-II, actuate Auto Shutdown (ASD) fuel system.
     Record fuel pressure gauge reading. Compare fuel pressure gauge
     reading with previous reading. If fuel pressure gauge reading is not
     at least 10 psi more than previous reading, go to step 4). If fuel
     pressure gauge reading is at least 10 psi more than previous reading,
     turn ignition off.

288. Inspect fuel lines between fuel filter and fuel rail for
     restriction. Repair as necessary. Perform TEST VER-1. If no
     restrictions are observed, replace fuel filter. Perform TEST VER-1.

289. Disconnect fuel return hose at fuel rail. Connect a 6-foot
     fuel hose to fuel rail. Put other end of 6-foot hose into an approved
     2-gallon or more capacity gasoline container. Turn ignition on. Using
     DRB-II, actuate fuel system.

CAUTION: DO NOT allow fuel pressure to exceed 70 psi (4.9 kg/cm) when squeezing fuel return hose.

5) Gently squeeze fuel return hose. Read fuel pressure gauge. Using DRB-II, stop fuel system actuator test. If pressure is more than 34 psi (2.3 kg/cm), replace fuel pressure regulator. Perform TEST VER-1. If it is less than 34 psi (2.3 kg/cm), replace fuel pump and sock filter. Perform TEST VER-1.

TEST NS-4B - CORRECTING FUEL DELIVERY

WARNING: High fuel pressure may be present in fuel lines. Open fuel system with caution. See FUEL PRESSURE RELEASE procedure.

290. Ensure fuel tank is at least 1/4 full. Release fuel
     pressure. Turn ignition off. Disconnect fuel return hose from fuel
     rail. Connect a 6-foot fuel hose to fuel rail. Put other end of 6-foot
     hose into an approved 2-gallon or more capacity gasoline container.

291. Turn ignition on. Using DRB-II, actuate fuel system. If
     pressure is less than 43 psi (3.0 kg/cm), go to next step. If
     pressure is more than 43 psi (3.0 kg/cm), replace fuel pressure
     regulator. Perform TEST VER-1.

292. Stop fuel system actuation. Turn ignition off. Reconnect
     fuel return hose. Remove fuel return hose from fuel tank. Connect Fuel
     Pressure Test Adapter (C-6541) to disconnected return hose.

293. Put other end of adapter hose into an approved 2-gallon or
     more capacity gasoline container. Turn ignition on. Using DRB-II,
     actuate fuel system. Read fuel pressure gauge. Using DRB-II stop
     actuation test.

294. If pressure is less than 43 psi (3.0 kg/cm), repair
     restricted fuel pump. Perform TEST VER-1. If pressure is more than 43
     psi (3.0 kg/cm), repair restricted fuel return line between fuel rail
     and fuel tank. Perform TEST VER-1.

TEST NS-5A - INSPECTING FUEL PUMP

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

295. Using DRB-II, stop actuation test. Using DRB-II, actuate
     Auto Shutdown (ASD) relay. Touch fuel pump relay. If fuel pump relay
     does not pulsate when actuated, go to TEST NS-5B. If fuel pump relay
     pulsates when actuated, turn ignition off.

296. Disconnect fuel pump relay. Using DRB-II in voltmeter
     mode, check voltage on fuel pump relay connector, battery voltage
     circuit (Red wire on XJ and ZJ bodies or Red/White wire on YJ body).
     If voltage is less than 10 volts, repair open circuit in Red wire on
     XJ and ZJ bodies or Red/White wire on YJ body. Perform TEST VER-1. If
     voltage is more than 10 volts, reconnect fuel pump relay.

297. Disconnect fuel pump harness connector. Ensure fuel pump
     connector has clean and tight connections. Turn ignition on. Using
     DRB-II, actuate fuel system. While still actuating, put DRB-II in
     voltmeter mode. Using DRB-II, check voltage on fuel pump connector,
     output wire(Dark Green/Orange wire on XJ body, Dark Green/Black wire
     on YJ body or Orange/Black wire on ZJ body). If voltage is less than
     10 volts, go to step 5). If voltage is more than 10 volts, stop
     actuation test.

298. Using DRB-II in ohmmeter mode, check resistance of fuel
     pump connector, ground circuit (Black wire on XJ and ZJ bodies or
     Black/Orange wire on YJ body). If resistance is more than 5 ohms,
     repair open in Black wire on XJ and ZJ bodies or Black/Orange wire on
     YJ body. Perform TEST VER-1. If resistance is less than 5 ohms,
     replace fuel pump. Perform TEST VER-1.

299. Turn ignition off. Disconnect fuel pump relay. Connect a

jumper wire between fuel pump relay connector, output circuit (Dark Green/Orange wire on XJ body, Dark Green/Black wire on YJ body or Orange/Black wire on ZJ body) and ground.

300. Using DRB-II in ohmmeter mode, check resistance of fuel
     pump connector, output circuit (Dark Green/Black wire on XJ and YJ
     bodies or Orange/Dark Blue wire on ZJ body). If resistance is less
     than 5 ohms, replace fuel pump relay. Perform TEST VER-1. On YJ and ZJ
     bodies, if resistance is more than 5 ohms, repair open in Dark
     Green/Black wire on YJ body or Orange/Dark Blue wire on ZJ body.
     Perform TEST VER-1.

301. On XJ body, disconnect ballast resistor. Using an external
     ohmmeter, check resistance of ballast resistor. If resistance is more
     than 5 ohms, replace ballast resistor. Perform TEST VER-1. If
     resistance is less than 5 ohms, repair open in Dark Green/Orange wire.
     Perform TEST VER-1.

TEST NS-5B - INSPECTING FUEL PUMP

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

302. Stop actuation test. Turn ignition off. Disconnect fuel
     pump relay. Turn ignition on. Using DRB-II, check voltage on fuel pump
     relay connector, ignition 12-volt supply circuit (Dark Blue wire on XJ
     body, White/Yellow wire on YJ body or Light Blue/Red wire on ZJ body).

303. If voltage is less than 10 volts, repair open in Dark Blue
     wire on XJ body, White/Yellow wire on YJ body or Light Blue/Red wire
     on ZJ body. Perform TEST VER-1. If voltage is more than 10 volts, go
     to next step.

304. Using an external ohmmeter, check resistance across fuel
     pump relay terminals. See CONNECTOR IDENTIFICATION at beginning of
     article. If resistance is more than 100 ohms, replace fuel pump relay.
     Perform TEST VER-1. If resistance is less than 100 ohm, repair open in
     Dark Blue/Yellow wire on XJ and YJ bodies or Pink wire on ZJ body.
     Perform TEST VER-1.

TEST NS-6A - CORRECTING NO RESPONSE CONDITION

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

305. If vehicle starts, go to TEST NS-6B. If vehicle does not
     start, turn ignition off. Disconnect Throttle Position Sensor (TPS)
     connector. Turn ignition on.

306. Using DRB-II in voltmeter mode, check voltage on TPS
     connector, 5-volt supply circuit (Violet/White wire). If voltage is
     more than 6 volts, repair open ground circuits at Powertrain Control
     Module (PCM) connector terminals No. 5 (Black/White wire on XJ and YJ
     bodies or Black/Tan wire on ZJ body), No. 11 and No. 12 (Black/Tan
     wire on XJ and ZJ bodies or Black wire on YJ body). Perform TEST VER-
     1. If voltage is less than 6 volts, go to next step.

307. If voltage is less than 4.4 volts, go to step 5). If
     voltage is more than 4.4 volts, reconnect TPS connector. Disconnect
     Manifold Absolute Pressure (MAP) sensor connector.

308. Using DRB-II, check voltage on MAP sensor connector, 5-
     volt supply circuit (Violet/White wire). If voltage is more than 4.4
     volts, go to TEST NS-6B. If voltage is less than 4.4 volts, replace
     TPS. Perform TEST VER-1.

309. Disconnect MAP sensor electrical connector. Using DRB-II,

check voltage on TPS connector, 5-volt supply circuit (Violet/White wire). If voltage is more than 4.4 volts, replace MAP sensor. Perform TEST VER-1.

310. If voltage is less than 4.4 volts, turn ignition off.
     Disconnect PCM connector. Using DRB-II in ohmmeter mode, check
     resistance of PCM connector terminal No. 6, 5-volt supply circuit
     (Violet/White wire).

311. If resistance is less than 5 ohms, repair short to ground
     in Violet/White wire. Perform TEST VER-1. If resistance is more than 5
     ohms, turn ignition on. Using DRB-II in voltmeter mode, check voltage
     on PCM connector terminal No. 9, ignition 12-volt feed circuit (Dark
     Blue wire on XJ body, White/Yellow wire on YJ body or Light Blue/Red
     wire on ZJ body).

312. If voltage is more than 10 volts, go to next step. If
     voltage is less than 10 volts, repair open in Dark Blue wire on XJ
     body, White/Yellow wire on YJ body or Light Blue/Red wire on ZJ body
     between PCM connector and ignition switch. Perform TEST VER-1.

313. Using DRB-II, check voltage on PCM connector terminal No.
     3, battery voltage circuit (Red wire on XJ and ZJ bodies or Red/White
     wire on YJ body). If voltage is less than 10 volts, go to next step.
     If voltage is more than 10 volts, replace PCM. Perform TEST VER-1.

10) Remove engine control fuse from Power Distribution Center
(PDC). Inspect fuse. If fuse is okay, go to next step. If fuse is

blown, go to step 12). Using DRB-II in voltmeter mode, check voltage on battery voltage side of PDC engine control fuse socket.

314. If voltage is more than 10 volts, repair open in Red wire
     on XJ and ZJ bodies or Red/White wire on YJ body between PDC engine
     control fuse socket and PCM connector terminal No. 3. Perform TEST
     VER-1. If voltage is less than 10 volts, repair open in battery
     voltage side of PDC engine control fuse socket. Perform TEST VER-1.

315. Turn ignition off. Disconnect Auto Shutdown (ASD) and
     fuel pump relays. Using DRB-II in ohmmeter mode, check resistance of
     PCM connector terminal No. 3, fused battery voltage circuit (Red wire
     on XJ and ZJ bodies or Red/White wire on YJ body). If resistance is
     less than 5 ohms, repair short to ground in Red wire on XJ and ZJ
     bodies or Red/White wire on YJ body. Perform TEST VER-1.

316. If resistance is more than 5 ohms, check resistance of
     ASD relay connector, output circuit (Dark Green/Orange wire). If
     resistance is less than 5 ohms, go to next step. If resistance is more
     than 5 ohms, perform TEST NS-6C.

317. Disconnect ignition coil connector. Using DRB-II, check
     resistance of ASD relay connector, output circuit (Dark Green/Orange
     wire). If resistance is more than 5 ohms, replace ignition coil.
     Perform TEST VER-1.

318. If resistance is less than 5 ohms, disconnect generator
     field connector. Using DRB-II, check resistance of ASD relay
     connector, output circuit (Dark Green/Orange wire). If resistance is
     more than 5 ohms, repair short to ground in generator. Perform TEST
     VER-1.

319. If resistance is less than 5 ohms, disconnect No. 1 fuel
     injector harness connector. Using DRB-II, check resistance of ASD
     relay connector, output circuit (Dark Green/Orange wire). If
     resistance is more than 5 ohms, replace No. 1 fuel injector. Perform
     TEST VER-1.

320. If resistance is less than 5 ohms, perform previous step
     for each additional fuel injector in order. After all injectors have
     been tested, if resistance is less than 5 ohms, repair short to ground
     in Dark Green/Orange wire. Perform TEST VER-1.

TEST NS-6B - CORRECTING NO RESPONSE CONDITION

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams,

see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

1) If ignition was not on when NO RESPONSE message was

displayed, turn ignition on to get a response. If ignition was on when NO RESPONSE message was displayed, turn ignition off.

321. Disconnect DRB-II from engine diagnostic connector.
     Disconnect Powertrain Control Module (PCM) connector. Using an
     external ohmmeter, check resistance between engine diagnostic
     connector, SCI transmit circuit (Pink wire on XJ and YJ bodies or
     Black wire on ZJ body) and ground.

322. If resistance is less than 5 ohms, repair short to ground
     in Pink wire on XJ and YJ bodies or Black wire on ZJ body. Perform
     TEST VER-1. If resistance is more than 5 ohms, using an external
     ohmmeter, check resistance between engine diagnostic connector, SCI
     receive circuit (Light Green wire on XJ and YJ bodies or Black/Yellow
     wire on ZJ body), and ground.

323. If resistance is less than 5 ohms, repair short to ground
     in Light Green wire on XJ and YJ bodies or Black/Yellow wire on ZJ
     body. Perform TEST VER-1. If resistance is more than 5 ohms, go to
     next step.

324. Using an external ohmmeter, check resistance of SCI
     transmit circuit (Pink wire on XJ and YJ bodies or Black wire on ZJ
     body) between engine diagnostic connector and PCM connector terminal
     No. 25. If resistance is more than 5 ohms, repair open in Pink wire on
     XJ and YJ bodies or Black wire on ZJ body. Perform TEST VER-1.

325. If resistance is less than 5 ohms, using an external

ohmmeter, check resistance of SCI receive circuit (Light Green wire on XJ and YJ bodies or Black/Yellow wire on ZJ body) between engine diagnostic connector and PCM connector terminal No. 45. If resistance is more than 5 ohms, repair open in Light Green wire on XJ and YJ bodies or Black/Yellow wire on ZJ body. Perform TEST VER-1.

326. If resistance is less than 5 ohms, connect DRB-II to a
     functional engine diagnostic connector on another vehicle. Turn
     ignition on. Using DRB-II, attempt to read fault messages. If DRB-II
     does not display NO RESPONSE, replace PCM on initial vehicle. Perform
     TEST VER-1.

327. If DRB-II displays NO RESPONSE, substitute another DRB-II
     cartridge. Using DRB-II, attempt to read fault messages. If DRB-II
     does not display NO RESPONSE, replace DRB-II cartridge. If DRB-II
     displays NO RESPONSE, substitute another DRB-II adapter cable. Using
     DRB-II, attempt to read fault messages. If DRB-II does not display NO
     RESPONSE, replace DRB-II adapter cable. If DRB-II displays NO
     RESPONSE, replace DRB-II or cartridge.

TEST NS-6C - CORRECTING NO RESPONSE CONDITION

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

328. Disconnect fuel pump connector and oxygen sensor
     connector. Using DRB-II, check resistance of fuel pump connector,
     output circuit (Dark Green/Black wire on XJ and YJ bodies or
     Orange/Dark Blue wire on ZJ body). If resistance is less than 5 ohms,
     repair short to ground in Dark Green/Black wire on XJ and YJ bodies or
     Orange/Dark Blue wire on ZJ body. Perform TEST VER-1.

329. If resistance is more than 5 ohms, using DRB-II, check
     resistance of oxygen sensor connector, relay output circuit (White
     wire). If resistance is more than 5 ohms, replace fuel pump. Perform
     TEST VER-1. If resistance is less than 5 ohms, replace oxygen sensor.
     Perform TEST VER-1.

TEST NS-7A - INSPECTING IDLE AIR CONTROL MOTOR OPERATION

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

330. Disconnect Idle Air Control (IAC) motor connector. Turn
     ignition on. Using DRB-II, actuate IAC motor. Using DRB-II in
     voltmeter mode, check voltage on IAC motor connector, No. 3 driver
     circuit (Gray/Red wire on XJ and YJ bodies or Yellow/Black wire on ZJ
     body). If voltage is less than one volt, go to TEST NS-7B.

331. If voltage is more than one volt, check voltage on IAC
     motor connector, No. 1 driver circuit (Brown/White wire). If voltage
     is less than one volt, go to TEST NS-7C. If voltage is more than one
     volt, check voltage on IAC motor connector, No. 4 driver circuit

(Violet/Black wire on XJ and YJ bodies or Gray/Red wire on ZJ body). If voltage is less than one volt, go to TEST NS-7D.

332. If voltage is more than one volt, check voltage on IAC
     motor connector, No. 2 driver circuit (Yellow/Black wire on XJ and YJ
     bodies or Violet/Black wire on ZJ body). If voltage is less than one
     volt, go to TEST NS-7E. If voltage is more than one volt, turn
     ignition off.

333. Remove IAC motor from throttle body. Reconnect IAC motor
     connector. Using DRB-II, actuate IAC motor. If IAC motor tip moves in
     and out, go to TEST NS-8A. If IAC motor tip does not move in and out,
     replace IAC motor. Perform TEST VER-1.

TEST NS-7B - INSPECTING IDLE AIR CONTROL MOTOR OPERATION

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

334. Turn ignition off. Disconnect Powertrain Control Module
     (PCM) connector. Inspect all terminals. Repair as necessary. Perform
     TEST VER-1. If PCM terminals are okay, go to next step.

335. Using an external ohmmeter, check resistance of No. 3
     driver circuit (Gray/Red wire on XJ and YJ bodies or Yellow/Black wire
     on ZJ body) between IAC motor connector and PCM connector terminal No.
     39. If resistance is less than 5 ohms, replace PCM. Perform TEST VER-
     1. If resistance is more than 5 ohms, repair open in Gray/Red wire on
     XJ and YJ bodies or Yellow/Black wire on ZJ body. Perform TEST VER-1.

TEST NS-7C - INSPECTING IDLE AIR CONTROL MOTOR OPERATION

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

336. Turn ignition off. Disconnect Powertrain Control Module
     (PCM) connector. Inspect all terminals. Repair as necessary. Perform
     TEST VER-1. If PCM terminals are okay, go to next step.

337. Using an external ohmmeter, check resistance of No. 1
     driver circuit (Brown/White wire) between IAC motor connector and PCM
     connector terminal No. 40. If resistance is less than 5 ohms, replace
     PCM. Perform TEST VER-1. If resistance is more than 5 ohms, repair
     open in Brown/White wire. Perform TEST VER-1.

TEST NS-7D - INSPECTING IDLE AIR CONTROL MOTOR OPERATION

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

338. Turn ignition off. Disconnect Powertrain Control Module
     (PCM) connector. Inspect all terminals. Repair as necessary. Perform
     TEST VER-1. If PCM terminals are okay, go to next step.

339. Using an external ohmmeter, check resistance of No. 4
     driver circuit (Violet/Black wire on XJ and YJ bodies or Gray/Red wire
     on ZJ body) between IAC motor connector and PCM connector terminal No.
     59. If resistance is less than 5 ohms, replace PCM. Perform TEST VER-
     1. If resistance is more than 5 ohms, repair open in Violet/Black wire
     on XJ and YJ bodies or Gray/Red wire on ZJ body. Perform TEST VER-1.

TEST NS-7E - INSPECTING IDLE AIR CONTROL MOTOR OPERATION

NOTE: For connector terminal identification, see CONNECTOR

IDENTIFICATION at beginning of article. For wiring diagrams, see L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

340. Turn ignition off. Disconnect Powertrain Control Module
     (PCM) connector. Inspect all terminals. Repair as necessary. Perform
     TEST VER-1. If PCM terminals are okay, go to next step.

341. Using an external ohmmeter, check resistance of No. 2
     driver circuit (Yellow/Black wire on XJ and YJ bodies or Violet/Black
     wire on ZJ body) between IAC motor connector and PCM connector
     terminal No. 60. If resistance is less than 5 ohms, replace PCM.
     Perform TEST VER-1. If resistance is more than 5 ohms, repair open in
     Yellow/Black wire on XJ and YJ bodies or Violet/Black wire on ZJ body.
     Perform TEST VER-1.

TEST NS-8A - CORRECTING START & STALL CONDITION

At this point in diagnostic test procedure, all engine control systems have been determined to be operating as designed and not causing a start and stall problem. Check following items as possible causes:

65535. Check if any MITCHELL (R) TECH SERVICE BULLETINS (TSBs) apply
       to vehicle.

65536. Check engine compression.

65537. Check for exhaust system restriction.

65538. Check camshaft and crankshaft sprockets.

65539. Check valve timing.

65540. Check for fuel contamination.

65541. Check secondary ignition system.

65542. Ensure PCV system is functioning properly.

TEST VER-1 - VERIFICATION TEST VER-1

342. Inspect vehicle to ensure all engine components are
     connected. Reassemble and reconnect components as necessary. Inspect
     engine oil for fuel contamination. Change oil and filter if necessary.
     Attempt to start engine.

343. If engine does not start, check if any MITCHELL(R) TECH
     SERVICE BULLETINS (TSBs) apply to vehicle and return to TEST FC-1A, if
     necessary.

344. If engine starts and Powertrain Control Module (PCM) was

changed, repair is complete.

4) If engine starts and PCM was not changed, connect DRB-II to engine diagnostic connector and erase fault messages. Repair is complete.

TEST VER-2 - VERIFICATION TEST VER-2

Inspect vehicle to ensure all engine components are connected. Reassemble and reconnect components as necessary. If another fault was read previously and not corrected, return to TEST FC-1A and follow path specified by other fault. If Powertrain Control Module (PCM) has not been replaced, perform following:

65535. Connect DRB-II to engine diagnostic connector, and erase
       faults.

65536. Using DRB-II, reset all values in adaptive memory.

65537. Disconnect DRB-II.

To ensure no other fault remains, perform following:

345. If vehicle is equipped with A/C, turn on A/C and blower
     motor. Drive vehicle for at least 5 minutes and attain a speed of at
     least 40 MPH. Ensure transmission shifts through all gears.

346. Upon completion of road test, turn engine off. Restart
     engine and let idle for at least 2 minutes. Turn engine off. Connect
     DRB-II to engine diagnostic connector.

347. Read all fault messages. If repaired fault has reset,
     repair is not complete. Check all pertinent MITCHELL(R) TECH SERVICE
     BULLETINS (TSBs), and return to TEST FC-1A if necessary. If another
     fault exists, return to TEST FC-1A and follow path specified by other
     fault. If no other faults exist, repair is now complete.