check engine light JEEP CHEROKEE 1994 Service Owner's Guide

TURN SIGNALS AND HAZARD WARNING FLASHER
CONTENTS
page page
HAZARD LAMPSÐXJ.................... 1
HAZARD LAMPSÐYJ.................... 2
TURN SIGNALSÐXJ..................... 1TURN SIGNALSÐYJ..................... 2
TURN/HAZARD SWITCH REPLACEMENT - ALL
MODELS............................. 3
TURN SIGNALSÐXJ
Refer to Section 8W - Wiring Diagrams for cir-
cuit wiring diagram.
DESCRIPTION
With the turn signal lever in its up or down posi-
tion and the ignition switch in ACCESSORY or ON,
current flows through the:
²turn/hazard switch
²selected turn indicator bulb
²front and rear turn signal bulbs
²and the front side marker bulb.
With the headlamps OFF, the turn and front side
marker lamps flash in unison.With the headlamps
ON, the turn and front side marker lamps flash al-
ternately.
DIAGNOSISÐTURN SIGNAL INOPERATIVE
(1) A turn signal indicator that does not flash usu-
ally indicates a burned out turn signal bulb. Check
for and replace if defective. System should now func-
tion properly. If not, go to next step.
High generator output voltage can burn out
lamps rapidly.(2) Remove and inspect 20 amp #8 fuse. Replace if
necessary. If OK, go to next step.
(3) Remove turn flasher, light blue can, located in
upper left corner of fuse block.
(4) Turn ignition switch to ACCESSORY. Check
for battery voltage at flasher bottom cavity on fuse
block. If OK, go to next step. If not, repair open cir-
cuit in wiring between turn flasher and #8 fuse.
(5) Turn ignition switch to ACCESSORY. Move
turn signal lever up or down. Replace turn flasher
with known good flasher. The lamps should flash. If
not, replace original flasher and go to next step.
(6) Turn ignition switch to OFF. Follow procedure
for turn/hazard switch replacement to locate steering
column connector. Unplug connector.
(7) Turn ignition switch to ACCESSORY. Check
for battery voltage at connector terminal L. If OK,
replace turn/hazard switch and check that lamps
flash. If not, repair open circuit in wiring between
turn flasher and steering column connector terminal
L.
HAZARD LAMPSÐXJ
Refer to Section 8W - Wiring Diagrams for cir-
cuit wiring diagram.
DESCRIPTION
With the hazard switch ON, current flows through
the:
²hazard flasher
²the turn/hazard switch
²two front turn signal bulbs
²two rear turn signal bulbs
²two front side marker bulbs
²and two turn indicator bulbs.
All of these bulbs will flash on and off.
DIAGNOSISÐHAZARD LAMPS INOPERATIVE
(1) Inspect 20 amp #F13 fuse in Power Distribu-
tion Center (PDC). The PDC is located in the engine
compartment, passenger side. For location of fuse,check underside of PDC cover. Replace if necessary.
If OK, go to next step.
(2) Remove hazard flasher (tin can) located in fuse
block.
(3) Check for battery voltage at the terminal on
the right (3 o'clock). If OK, go to next step. If not, re-
pair open circuit in wiring between #F13 fuse and
hazard flasher right terminal.
(4) Replace hazard flasher with known good
flasher. Activate hazard warning switch. Lamps
should flash. If not, replace original flasher and go to
next step.
(5) Follow procedure for turn/hazard switch re-
placement to locate steering column connector. Un-
plug connector.
(6) Check for battery voltage at connector terminal
K. If OK, replace turn/hazard switch. If not, repair
open circuit in wiring between hazard flasher and
steering column connector terminal K.
JTURN SIGNALS AND HAZARD WARNING FLASHER 8J - 1

TURN SIGNALSÐYJ
Refer to Section 8W - Wiring Diagrams for cir-
cuit wiring diagram.
DESCRIPTION
With the turn signal lever in its up or down posi-
tion and the ignition switch in ACCESSORY or ON,
current flows through the:
²turn/hazard switch
²selected turn indicator bulb
²front and rear turn signal bulbs
²front side marker bulb
With the headlamps OFF, the turn and side
marker lamps flash in unison.With the headlamps
ON, the turn and side marker lamps flash alter-
nately.
DIAGNOSINGÐTURN SIGNAL INOPERATIVE
(1) A turn signal indicator that does not flash usu-
ally indicates a burned out turn signal bulb. Check
for and replace if defective. System should now func-
tion properly. If not, go to next step.
High generator output voltage can burn out
lamps rapidly.
(2) Locate fuse block under driver's side of instru-
ment panel.(3) Remove and inspect 15 amp #4 fuse. Replace if
necessary. If OK, go to next step.
(4) Remove turn flasher, light blue can, located in
fuse block.
(5) Turn ignition switch to ACCESSORY. Check
for battery voltage at cavity on left (closest to hazard
flasher can). If OK, go to next step. If not, repair
open circuit in wiring between turn flasher and #4
fuse.
(6) Turn ignition switch to ACCESSORY. Move
turn signal lever up or down. Replace turn flasher
with known good flasher. The lamps should flash. If
not, replace original flasher and go to next step.
(7) Turn ignition switch to OFF. Follow procedure
for turn/hazard switch replacement to locate steering
column connector. Unplug connector.
(8) Turn ignition switch to ACCESSORY. Check
for battery voltage at connector terminal L. If OK,
replace turn/hazard switch. If not, repair open circuit
in wiring between turn flasher and steering column
connector terminal L.
HAZARD LAMPSÐYJ
Refer to Section 8W - Wiring Diagrams for cir-
cuit wiring diagram.
DESCRIPTION
With the hazard switch ON, current flows through
the:
²hazard flasher
²turn/hazard switch
²two front turn signal bulbs
²two rear turn signal bulbs
²two front side marker bulbs
²two turn indicator bulbs.
All of these bulbs will flash on and off.
DIAGNOSISÐHAZARD LAMPS INOPERATIVE
(1) Inspect 20 amp #F5 fuse in Power Distribution
Center (PDC). The PDC is located in the engine com-
partment, passenger side. For location of fuse, check
underside of PDC cover. Replace if necessary. If OK,
go to next step.(2) Remove hazard flasher (tin can) located in fuse
block.
(3) Check for battery voltage at the terminal on
the left. If OK, go to next step. If not, repair open cir-
cuit in wiring between #F5 fuse and hazard flasher
left terminal.
(4) Replace hazard flasher with known good
flasher. Activate hazard warning switch. Lamps
should flash. If not, replace original flasher and go to
next step.
(5) Follow procedure for turn/hazard switch re-
placement to locate steering column connector. Un-
plug connector.
(6) Check for battery voltage at connector terminal
K. If OK, replace turn/hazard switch. If not, repair
open circuit in wiring between hazard flasher and
steering column connector terminal K.
8J - 2 TURN SIGNALS AND HAZARD WARNING FLASHERJ

(2) Install the mounting screws.
(3) Connect the wiring harness.
(4) Install the pivot pin, seal, bezel and attaching
nut (Fig. 2). Torque nut to 4 Nzm (32 in. lbs.).
(5) Connect interior washer hose.
Lubricate the bezel nipples with a small amount
of water and then install the washer hoses.
(6) Install the liftgate trim panel.
(7) Install the wiper arm assembly and connect the
external washer hose to the bezel.
(8) Slide the clip along the hose until it is over
hose mount.
The blade should be parallel to window open-
ing and no closer than 5mm to window seal
when operated on a wet window (Fig. 3).
WASHER PUMP REPLACEMENT
The washer pump for the liftgate is located next to
the front washer pump on the washer reservoir in
the engine compartment. For replacement refer to
the front washer pump replacement procedure.
LIFTGATE WIPER SWITCH REPLACEMENT
(1) Remove the instrument panel bezel; see Instru-
ment Panel and Components Section for the proce-
dure.
(2) Remove the switch housing panel.
(3) Unplug the switch connector. Slightly depress
the switch mounting tabs and remove the switch
(Fig. 4).
DIAGNOSING REAR WIPER
(1) Remove and inspect 25 amp, #1 fuse. Replace
as required.
(2) Turn ignition switch to ACCESSORY and rear
wiper switch to WASH.
²Measure voltage at rear wiper switch terminal B.
Meter should read battery voltage. If not, repair open
to #1 fuse.
²Measure voltage at rear wiper switch terminals A,
C and D. Meter should read battery voltage. If not,
replace switch.(3) Turn ignition switch to ACCESSORY, place
rear wiper switch in WIPE. Measure voltage at rear
wiper switch terminal C. Meter should read battery
voltage. If not, replace switch.
(4) Remove liftgate cover and measure resistance
from rear wiper motor terminal 1 to a good ground.
Meter should read zero ohms. If not, repair open to
ground splice.
(5) Turn ignition switch to ACCESSORY and rear
wiper switch to WASH.
²Measure voltage at motor connector terminals 2, 3
and 4. Meter should read battery voltage. If OK, re-
place wiper motor. If not, repair open(s) to rear wiper
switch.
DIAGNOSING REAR WIPER WASHER
(1) Turn ignition switch to ACCESSORY and place
rear wiper/washer switch in WASH.
²Operate rear wiper motor. If motor does not oper-
ate check the 25 amp #1 fuse.
(2) Turn ignition switch to ACCESSORY and un-
plug rear washer pump connector.
²Measure resistance at pump connector terminal B
(ignition switch OFF). Meter should read zero ohms.
If not, repair open to ground.
²Measure voltage at pump connector terminal A,
switch in WASH. Meter should read battery voltage.
If OK, replace pump. If not, go to step 3.
(3) Remove switch and reconnect below instrument
panel. Backprobe switch connector with ignition
switch in ACCESSORY.
²Measure voltage at switch connector terminal B.
Meter should read battery voltage. If not, repair open
to fuse.
²Measure voltage at switch connector terminal A,
switch in WASH. Meter should read battery voltage.
If not, replace switch.
Fig. 3 Rear Wiper Arm Positioning
Fig. 4 Rear Wiper Switch
8K - 6 WINDSHIELD WIPERSJ

WIRING DIAGRAMS XJ-RHD
INDEX
Wiring Diagram Name Sheet Number
A/C Compressor Clutch........................45
A/C Compressor Clutch Relay....................45
A/C Heater Blower Motor.......................46
A/C Low Pressure Switch.......................45
A/C Mode Selector Switch.......................46
A/C System.............................45, 46
A/C Thermostat..............................45
Antenna Mast...............................47
Ashtray Illumination Lamp.......................26
Automatic Shut Down Relay......................9
Back-up Lamp Switch.........................16
Battery....................................6
Blower Motor............................44, 46
Blower Resistor...........................44, 46
Blower Switch............................44, 46
Body Ground...............................59
Brake Warning Switch.........................42
Camshaft Position Sensor.......................12
Cargo Lamp................................30
Charging System.............................5
Generator.................................5
Check Engine Indicator Lamp..................39, 40
Chime Module..............................43
Chime Module Connector.......................71
Cigar Lighter...............................58
Circuit Breakers
Windshield Wiper Circuit Breaker...............2,33
Connectors
Chime Module Connector......................71
Dash to Instrument Panel Connector A.............64
Dash to Instrument Panel Connector B.............65
Dash to Instrument Panel Connector C.............66
Data Link Connector.........................10
Instrument Cluster Connector 16 Way...........37, 69
Main Body Connector 1.......................70
Power Mirror Connector......................61
Powertrain Control Module Connector..............73
Steering Column Connector 11 Way...............67
Telltale Connector........................38, 68
Transmission Control Module Connector............72
Transmission Data Link Connector................17
Coolant Temperature Switch......................16
Crankshaft Position Sensor......................12
Dash to Instrument Panel Connector A..............64
Dash to Instrument Panel Connector B..............65
Dash to Instrument Panel Connector C..............66
Data Link Connector..........................10
Distributor Ignition Coil........................10
Dome Lamp................................31
Dome and Courtesy Lamps.................29, 30, 31
Cargo Lamp..............................30
Dome Lamp..............................31Wiring Diagram Name Sheet Number
Dome/Reading Lamp.........................31
Glove Box Lamp...........................29
Reading Lamp.............................31
Vanity Lamps.............................31
Dome/Reading Lamp..........................31
Door Jamb Switch System....................49, 50
Left Front Door Jamb Switch...................50
Left Rear Door Jamb Switch...................50
Liftgate Switch............................46
Right Front Door Jamb Switch..................49
Right Rear Door Jamb Switch..................49
Electronic Fuel Injection
Ignition System................9,10,11,12,13,14
Automatic Shut Down Relay.....................9
Camshaft Position Sensor.....................12
Crankshaft Position Sensor.....................12
Data Link Connector.........................10
Distributor Ignition Coil.......................10
Engine Coolant Temperature Sensor...............11
Fuel Injectors.............................14
Fuel Pump Relay............................9
Heated Oxygen Sensor.......................13
Idle Air Control Motor........................14
Intake Air Temp Sensor.......................11
Map Sensor..............................11
Powertrain Control Module........9,10,11,12,13,14
Throttle Position (Sensor).....................11
Engine Block Heater...........................58
Engine Coolant Temperature Sensor................11
Engine Coolant Temperature Switch.................15
Engine Oil Pressure and Temperature System..........15
Engine Oil Pressure Switch......................15
Engine Starter System..........................6
Battery..................................6
Engine Starter Motor.........................6
Engine Starter Relay..........................6
Fan Control Relay...........................3,7
Fog Lamp Illumination Lamp.....................20
Fog Lamp Relay.............................21
Fog Lamp Switch............................20
4WD Select Trac Indicator Lamp................39, 40
Front Axle Switch............................16
Front End Lighting.........................21, 22
Fog Lamp Relay...........................21
Left Fog Lamp.............................21
Left Headlamp.............................21
Left Park/Turn Signal Lamp....................21
Left Side Marker Lamp.......................21
Right Fog Lamp............................22
Right Headlamp............................22
Right Park/Turn Signal Lamp...................22
Right Side Marker Lamp......................22
Front Wipers/Washer - Intermittent..............33, 34
JWIRING DIAGRAMS 8W - 271

Wiring Diagram Name Sheet Number
Front Washer Pump.........................34
Front Wiper Motor..........................34
Intermittent Wiper Module.....................33
Park Switch..............................34
Washer Fluid Level Switch.....................33
Washer Switch............................33
Windshield Wiper/Washer Circuit Breaker...........33
Wiper/Washer Switch........................33
Fuel Gauge Sensor...........................54
Fuel Injectors...............................14
Fuel Pump.................................54
Fuel Pump Module...........................54
Fuel Pump Relay............................3,9
Fuel Tank System............................54
Full Time Indicator Lamp.....................39, 40
Fuse Application Chart........................1,2
Fuse Panel..............................62, 63
Fuses
Fuse #2.............................2,4,60
Fuse #4..........................2,33,44,46
Fuse #5.............................1,4,27
Fuse #6.............................1,4,51
Fuse #9...............................1,19
Fuse #10..............................1,19
Fuse #13............................2,47,58
Fuse #14.........................2,23,33,60
Fuse #19............................2,33,35
Fuse #25............................1,19,25
Fuse #26..........................1,8,37,43
F1 ...................................3,4
F2 ...................................3,9
F3 ...................................3,17
F4 ...................................3,4
F5 .................................3,6,17
F6 .................................3,9,10
F7 .....................................3
F8 ...................................3,4
F9 .....................................3
F10 ...................................3,4
F11 ...................................3,4
F12 ...................................3,4
F13 ...................................3,4
F14 ...................................3,4
F15 ...................................3,4
F16 ...................................3,4
Generator..................................5
Glove Box Lamp.............................29
Hazard Flasher..............................32
Headlamp Dimmer Switch.......................19
Headlamp Switch...........................1,19
Headlamp Switch System.....................19, 20
Fog Lamp Illumination........................20
Fog Lamp Switch...........................20
Headlamp Dimmer Switch.....................19
Headlamp Switch...........................19
Headlamps..............................21, 22
Heated Oxygen Sensor.........................13
Heated Rear Window..........................60Wiring Diagram Name Sheet Number
Relay...................................60
Switch..................................60
Switch Illumination..........................25
Heater A/C Panel Lamp........................25
Heater and A/C System......................45, 46
A/C Compressor Clutch.......................45
A/C Compressor Clutch Relay...................45
A/C Heater Blower Motor......................46
A/C Low Pressure Switch.....................45
A/C Mode Selector Switch.....................46
A/C Thermostat............................45
Blower Resistor............................46
Blower Switch.............................46
Powertrain Control Module.....................45
Heater System..............................44
Blower Resistor............................44
Blower Switch.............................44
Heater Blower Motor.........................44
Heat Mode Select Switch......................44
Heater Blower Motor..........................44
Heater Element..............................52
Heavy Duty Cooling (4.0L).......................7
Fan Control Relay...........................7
Powertrain Control Module.....................7
Radiator Fan Motor..........................7
High-Beam Indicator Lamp......................41
Horn System...............................27
Horn Brush/Slip Ring........................27
Horn Relay...............................27
Horn Switch..............................27
Left Side Horn.............................27
Right Side Horn............................27
Idle Air Control Motor.........................14
Ignition Key Warning Switch.....................43
Ignition Switch...............................8
Ignition System..............................8
Instrument Cluster............................37
Instrument Cluster Connector.....................37
Instrument Cluster Connector 16 Way...............69
Instrument Cluster Indicator Printed Circuit Board.......40
Instrument Cluster Printed Circuit Board (Standard)......41
Instrument Panel Ground.......................32
Instrument Panel Illumination..................25, 26
Heated Rear Window Switch Illumination...........25
Heater A/C Panel Lamp.......................25
Rear Wiper/Wash Switch Lamp..................26
Transfer Case Lamp.........................26
Transmission Range Lamp.....................26
Intake Air Temp Sensor........................11
Intermittent Front Wipers/Washers...............33, 34
Intermittent Wiper Module.......................33
Lamps
Ashtray Illumination Lamp.....................26
Back-Up Lamp..........................55, 56
Cargo Lamp..............................30
Check Engine Indicator Lamp................39, 40
Cigar Lighter Illumination......................58
Dome Lamp..............................31
8W - 272 WIRING DIAGRAMSJ

can easily be wiped off. Components should be
torqued in place within 15 minutes. The use of a lo-
cating dowel is recommended during assembly to pre-
vent smearing the material off location.
ENGINE PERFORMANCE
To provide best vehicle performance and lowest ve-
hicle emissions, it is most important that the tune-up
be done accurately. Use the specifications listed on
the Vehicle Emission Control Information label
found on the engine compartment hood.
(1) Test battery specific gravity. Add water, if nec-
essary. Clean and tighten battery connections.
(2) Test cranking amperage draw (refer to Group
8B, Battery/Starter Service for the proper proce-
dures).
(3) Tighten the intake manifold bolts (refer to
Group 11, Exhaust System and Intake Manifold for
the proper specifications).
(4) Perform cylinder compression test:
(a) Check engine oil level and add oil, if neces-
sary.
(b) Drive the vehicle until engine reaches normal
operating temperature.
(c) Select a route free from traffic and other
forms of congestion, observe all traffic laws and
briskly accelerate through the gears several times.
The higher engine speed may help clean out valve
seat deposits which can prevent accurate compres-
sion readings.
CAUTION: DO NOT overspeed the engine.
(d) Remove all spark plugs from engine. As
spark plugs are being removed, check electrodes for
abnormal firing indicators - fouled, hot, oily, etc.
Record cylinder number of spark plug for future
reference.
(e) Disconnect coil wire from distributor and se-
cure to good ground to prevent a spark from start-
ing a fire.
(f) Be sure throttle blades are fully open during
the compression check.
(g) Insert compression gage adaptor into the
No.1 spark plug hole. Crank engine until maxi-
mum pressure is reached on gauge. Record this
pressure as No.1 cylinder pressure.
(h) Repeat Step 4g for all remaining cylinders.
(i) Compression should not be less than 689 kPa
(100 psi) and not vary more than 172 kPa (25 psi)
from cylinder to cylinder.
(j) If cylinder(s) have abnormally low compres-
sion pressures, repeat steps 4a through 4h.
(k) If the same cylinder(s) repeat an abnormally
low reading, it could indicate the existence of a
problem in the cylinder.
The recommended compression pressures are
to be used only as a guide to diagnosing engineproblems. An engine should NOT be disassem-
bled to determine the cause of low compression
unless some malfunction is present.
(5) Clean or replace spark plugs as necessary. Ad-
just gap (refer to Group 8D, Ignition System for gap
adjustment and torque).
(6) Test resistance of spark plug cables (refer to
Group 8D, Ignition System).
(7) Inspect the primary wire. Test coil output volt-
age, primary and secondary resistance. Replace parts
as necessary (refer to Group 8D, Ignition System and
make necessary adjustment).
(8) Set ignition timing to specifications (refer to
Specification Label on engine compartment hood).
(9) Perform a combustion analysis.
(10) Test fuel pump for pressure and vacuum (refer
to Group 14, Fuel System for the proper specifica-
tions).
(11) Inspect air filter element (refer to Group 0,
Lubrication and Maintenance for the proper proce-
dure).
(12) Inspect crankcase ventilation system (refer to
Group 0, Lubrication and Maintenance for the proper
procedure).
(13) For emission controls refer to Group 25, Emis-
sion Controls System for service procedures.
(14) Inspect and adjust accessory belt drives (refer
to Group 7, Cooling System for the proper adjust-
ments).
(15) Road test vehicle as a final test.
HONING CYLINDER BORES
Before honing, stuff plenty of clean shop towels un-
der the bores and over the crankshaft to keep abra-
sive materials from entering the crankshaft area.
(1) Used carefully, the Cylinder Bore Sizing Hone
C-823 equipped with 220 grit stones, is the best tool
for this job. In addition to deglazing, it will reduce
taper and out-of-round as well as removing light
scuffing, scoring or scratches. Usually a few strokes
will clean up a bore and maintain the required lim-
its.
CAUTION: DO NOT use rigid type hones to remove
cylinder wall glaze.
(2) Deglazing of the cylinder walls may be done if
the cylinder bore is straight and round. Use a cylin-
der surfacing hone, Honing Tool C-3501, equipped
with 280 grit stones (C-3501-3810). 20-60 strokes, de-
pending on the bore condition, will be sufficient to
provide a satisfactory surface. Using honing oil
C-3501-3880 or a light honing oil available from ma-
jor oil distributors.
CAUTION: DO NOT use engine or transmission oil,
mineral spirits or kerosene.
9 - 2 ENGINESJ

(3) Connect the CCV hoses (Fig. 1).
(4) Connect negative cable to battery.
ROCKER ARMS
This procedure can be done with the engine in or
out of the vehicle.
REMOVAL
(1) Remove the engine cylinder head cover.
(2) Remove the capscrews at each bridge and pivot
assembly (Fig. 2). Alternately loosen the capscrews
one turn at a time to avoid damaging the bridges.
(3) Check for rocker arm bridges which are caus-
ing misalignment of the rocker arm to valve tip area.
(4) Remove the bridges, pivots and corresponding
pairs of rocker arms (Fig. 2). Place them on a bench
in the same order as removed.
(5) Remove the push rods and place them on a
bench in the same order as removed.
CLEANING
Clean all the components with cleaning solvent.
Use compressed air to blow out the oil passages in
the rocker arms and push rods.
INSPECTION
Inspect the pivot surface area of each rocker arm.
Replace any that are scuffed, pitted, cracked or ex-
cessively worn.
Inspect the valve stem tip contact surface of each
rocker arm and replace any rocker arm that is deeply
pitted.
Inspect each push rod end for excessive wear and
replace as required. If any push rod is excessivelyworn because of lack of oil, replace it and inspect the
corresponding hydraulic tappet for excessive wear.
Inspect the push rods for straightness by rolling
them on a flat surface or by shining a light between
the push rod and the flat surface.
A wear pattern along the length of the push rod is
not normal. Inspect the engine cylinder head for ob-
struction if this condition exists.
INSTALLATION
(1) Lubricate the ball ends of the push rods with
Mopar Engine Oil Supplement, or equivalent and in-
stall push rods in their original locations. Ensure
that the bottom end of each push rod is centered in
the tappet plunger cap seat.
(2) Using Mopar Engine Oil Supplement, or equiv-
alent, lubricate the area of the rocker arm that the
pivot contacts. Install rocker arms, pivots and bridge
above each cylinder in their originally position.
(3) Loosely install the capscrews through each
bridge.
(4) At each bridge, tighten the capscrews alter-
nately, one turn at a time, to avoid damaging the
bridge. Tighten the capscrews to 28 Nzm (21 ft. lbs.)
torque.
(5) Install the engine cylinder head cover.
ENGINE CYLINDER HEAD
This procedure can be done with the engine in or
out of the vehicle.
REMOVAL
(1) Disconnect negative cable from battery.
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR
DRAIN COCK WITH THE SYSTEM HOT AND PRES-
SURIZED BECAUSE SERIOUS BURNS FROM THE
COOLANT CAN OCCUR.
(2) Drain the coolant and disconnect the hoses at
the engine thermostat housing. DO NOT waste reus-
able coolant. If the solution is clean and is being
drained only to service the engine or cooling system,
drain the coolant into a clean container for reuse.
(3) Remove the air cleaner assembly.
(4) Remove the engine cylinder head cover.
(5) Remove the capscrews, bridge and pivot assem-
blies and rocker arms (Fig. 2).
(6) Remove the push rods (Fig. 2).Retain the
push rods, bridges, pivots and rocker arms in
the same order as removed.
(7) Loosen the serpentine drive belt at the power
steering pump, if equipped or at the idler pulley (re-
fer to Group 7, Cooling System for the proper proce-
dure).
(8) If equipped with air conditioning, perform the
following:
Fig. 2 Rocker Arm Assembly
J2.5L ENGINE 9 - 19

(3) Check for rocker arm bridges which are caus-
ing misalignment of the rocker arm to valve tip area.
(4) Remove the bridges, pivots and corresponding
pairs of rocker arms (Fig. 2). Place them on a bench
in the same order as removed.
(5) Remove the push rods and place them on a
bench in the same order as removed.
CLEANING
Clean all the components with cleaning solvent.
Use compressed air to blow out the oil passages in
the rocker arms and push rods.
INSPECTION
Inspect the pivot surface area of each rocker arm.
Replace any that are scuffed, pitted, cracked or ex-
cessively worn.
Inspect the valve stem tip contact surface of each
rocker arm and replace any rocker arm that is deeply
pitted.
Inspect each push rod end for excessive wear and
replace as required. If any push rod is excessively
worn because of lack of oil, replace it and inspect the
corresponding hydraulic tappet for excessive wear.
Inspect the push rods for straightness by rolling
them on a flat surface or by shining a light between
the push rod and the flat surface.
A wear pattern along the length of the push rod is
not normal. Inspect the engine cylinder head for ob-
struction if this condition exists.
INSTALLATION
(1) Lubricate the ball ends of the push rods with
Mopar Engine Oil Supplement, or equivalent and in-
stall push rods in their original locations. Ensurethat the bottom end of each push rod is centered in
the tappet plunger cap seat.
(2) Using Mopar Engine Oil Supplement, or equiv-
alent, lubricate the area of the rocker arm that the
pivot contacts. Install rocker arms, pivots and bridge
above each cylinder in their originally position.
(3) Loosely install the capscrews through each
bridge.
(4) At each bridge, tighten the capscrews alter-
nately, one turn at a time, to avoid damaging the
bridge. Tighten the capscrews to 28 Nzm (21 ft. lbs.)
torque.
(5) Install the engine cylinder head cover.
ENGINE CYLINDER HEAD
This procedure can be done with the engine in or
out of the vehicle.
REMOVAL
(1) Disconnect negative cable from battery.
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR
DRAIN COCK WITH THE SYSTEM HOT AND PRES-
SURIZED BECAUSE SERIOUS BURNS FROM THE
COOLANT CAN OCCUR.
(2) Drain the coolant and disconnect the hoses at
the engine thermostat housing. DO NOT waste reus-
able coolant. If the solution is clean and is being
drained only to service the engine or cooling system,
drain the coolant into a clean container for reuse.
(3) Remove the air cleaner assembly.
(4) Remove the engine cylinder head cover.
(5) Remove the capscrews, bridge and pivot assem-
blies and rocker arms (Fig. 2).
(6) Remove the push rods (Fig. 2).Retain the
push rods, bridges, pivots and rocker arms in
the same order as removed.
(7) Loosen the serpentine drive belt at the power
steering pump, if equipped or at the idler pulley (re-
fer to Group 7, Cooling System for the proper proce-
dure).
(8) If equipped with air conditioning, perform the
following:
(a) Remove the bolts from the A/C compressor
mounting bracket and set the compressor aside.
(b) Remove the air conditioner compressor
bracket bolts from the engine cylinder head.
(c) Loosen the through bolt at the bottom of the
bracket.
(9) If equipped, disconnect the power steering
pump bracket. Set the pump and bracket aside. DO
NOT disconnect the hoses.
(10) Remove the fuel lines and vacuum advance
hose.
Fig. 2 Rocker Arm Assembly
9 - 60 4.0L ENGINEJ

ing the IAC motor pintle in and out of the air control
passage. The IAC motor is positioned when the igni-
tion key is turned to the On position.
A (factory adjusted) set screw is used to mechani-
cally limit the position of the throttle body throttle
plate.Never attempt to adjust the engine idle
speed using this screw.All idle speed functions are
controlled by the PCM.
IGNITION COILÐPCM OUTPUT
System voltage is supplied to the ignition coil pos-
itive terminal. The powertrain control module (PCM)
operates the ignition coil.Base (initial) ignition
timing is not adjustable.The PCM adjusts ignition
timing to meet changing engine operating conditions.
The ignition coil is located near the ignition distrib-
utor (Fig. 22).
Refer to Group 8D, Ignition System for additional
information.
MALFUNCTION INDICATOR LAMPÐPCM OUTPUT
The Malfunction Indicator Lamp (formerly referred
to as the Check Engine Lamp) illuminates on the in-
strument panel each time the ignition key is turned
on. It will stay on for three seconds as a bulb test.
If the powertrain control module (PCM) receives an
incorrect signal, or no signal from certain sensors or
emission related systems, the lamp is turned on. This
is a warning that the PCM has recorded a system or
sensor malfunction. In some cases, when a problem is
declared, the PCM will go into a limp-in mode. This
is an attempt to keep the system operating. It signals
an immediate need for service.
The lamp can also be used to display a Diagnostic
Trouble Code (DTC). Cycle the ignition switch On-
Off-On-Off-On within three seconds and any codes
stored in the PCM memory will be displayed. This is
done in a series of flashes representing digits. Refer
to On-Board Diagnostics in the General Diagnosis
section of this group for more information.
RADIATOR FAN RELAYÐPCM OUTPUT
XJ MODELS ONLY
The electric radiator cooling fan used in XJ models
(equipped with 4.0L engine, heavy duty cooling
and/or air conditioning) is controlled by the power-
train control module (PCM) through radiator fan re-
lay. The relay is energized when coolant temperature
is above 103ÉC (217ÉF). It will then de-energize when
coolant temperature drops to 98ÉC (208ÉF). Refer to
Group 7, Cooling Systems for more information.
The relay is located in the power distribution cen-
ter (PDC) (Fig. 23).
The electric radiator cooling fan is not used on YJ
models.
SCI TRANSMITÐPCM OUTPUT
SCI Transmit is the serial data communication
transmit circuit for the DRB scan tool. The power-
train control module (PCM) transmits data to the
DRB through the SCI Transmit circuit.
SHIFT INDICATORÐPCM OUTPUT
Vehicles equipped with manual transmissions have
an Up-Shift indicator lamp. The lamp is controlled
by the powertrain control module (PCM). The lamp
illuminates on the instrument panel to indicate when
the driver should shift to the next highest gear for
best fuel economy. The PCM will turn the lamp OFF
after 3 to 5 seconds if the shift of gears is not per-
formed. The up-shift light will remain off until vehi-
cle stops accelerating and is brought back to range of
up-shift light operation. This will also happen if ve-
hicle is shifted into fifth gear.
The indicator lamp is normally illuminated when
the ignition switch is turned on and it is turned off
when the engine is started up. With the engine run-
ning, the lamp is turned on/off depending upon en-
gine speed and load.
Fig. 23 PDCÐXJ Models
Fig. 22 Ignition CoilÐTypical
14 - 26 FUEL SYSTEMJ

IDLE AIR CONTROL MOTOR TEST
Idle Air Control (IAC) Motor operation can be
tested using special exerciser tool number 7558 (Fig.
42).
CAUTION: Proper safety precautions must be taken
when testing the idle air control motor:
²Set the parking brake and block the drive wheels
²Route all tester cables away from the cooling fans,
drive belt, pulleys and exhaust components
²Provide proper ventilation while operating the en-
gine
²Always return the engine idle speed to normal be-
fore disconnecting the exerciser tool
(1) With the ignition OFF, disconnect the IAC mo-
tor wire connector at throttle body (Fig. 42).
(2) Plug the exerciser tool number 7558 harness
connector into the IAC motor.
(3) Connect the red clip of exerciser tool 7558 to
battery positive terminal. Connect the black clip tonegative battery terminal. The red light on the exer-
ciser tool will flash when the tool is properly con-
nected.
(4) Start engine.
When the switch on the tool is in the HIGH or
LOW position, the light on the tool will flash. This
indicates that voltage pulses are being sent to the
IAC stepper motor.
(5) Move the switch to the HIGH position. The en-
gine speed should increase. Move the switch to the
LOW position. The engine speed should decrease.
(a) If the engine speed changes while using the
exerciser tool, the IAC motor is functioning prop-
erly. Disconnect the exerciser tool and connect the
IAC motor wire connector to the stepper motor.
(b) If the engine speed does not change, turn the
ignition OFF and proceed to step (6). Do not discon-
nect exerciser tool from the IAC motor.
(6) Remove the IAC motor from the throttle body.
Do not remove IAC motor housing from throttle
body.
CAUTION: When checking IAC motor operation with
the motor removed from the throttle body, do not
extend the pintle (Fig. 43) more than 6.35 mm (.250
in). If the pintle is extended more than this amount,
it may separate from the IAC motor. The IAC motor
must be replaced if the pintle separates from the
motor.
(7) With the ignition OFF, cycle the exerciser tool
switch between the HIGH and LOW positions. Ob-
serve the pintle. The pintle should move in-and-out
of the motor.
(a) If the pintle does not move, replace the idle
air control motor. Start the engine and test the re-
placement motor operation as described in step (5).
(b) If the pintle operates properly, check the idle
air control motor bore in the throttle body bore for
blockage and clean as necessary. Reinstall the idle
air control motor and retest. If blockage is not
Fig. 41 Oxygen SensorÐTypical
Fig. 42 IAC Motor TestingÐTypical
Fig. 43 Idle Air Control (IAC) Motor Pintle
14 - 46 FUEL SYSTEMJ