23 body JEEP GRAND CHEROKEE 2002 WJ / 2.G Workshop Manual

are only serviced as a unit with the right headlamp
and dash wire harness. If the PDC main housing
unit, fuse wedges or the bus bars are faulty or dam-
aged, the right headlamp and dash wire harness unit
must be replaced.
OPERATION
All of the current from the battery and the generator
output enters the PDC through two cables and a single
two-holed eyelet that is secured with nuts to the two
PDC B(+) terminal studs just inside the front end of the
PDC housing. The PDC cover is unlatched and opened
to access the battery and generator output connection
B(+) terminal studs, the fuses or the relays. Internal
connection of all of the PDC circuits is accomplished by
an intricate combination of hard wiring and bus bars.
Refer toPower Distribution
in Wiring Diagrams for
the location of complete PDC circuit diagrams.
REMOVAL
The Power Distribution Center (PDC) main housing
unit, the PDC fuse wedges and the PDC bus bars can-
not be repaired and are only serviced as a unit with the
right headlamp and dash wire harness. If the PDC
main housing unit, the fuse wedges or the bus bars are
faulty or damaged, the entire PDC and right headlamp
and dash wire harness unit must be replaced.
(1)Disconnect and isolate the battery negative cable.
(2) Disconnect each of the right headlamp and
dash wire harness connectors. Refer toConnector
Locationsin Wiring Diagrams for the location of
more information on the right headlamp and dash
wire harness connector locations.
(3) Remove all of the fasteners that secure each of
the right headlamp and dash wire harness ground
eyelets to the vehicle body and chassis components.
Refer toConnector Locationsin Wiring Diagrams
for the location of more information on the ground
eyelet locations.
(4) Disengage each of the retainers that secure the
right headlamp and dash wire harness to the vehicle
body and chassis components. Refer toConnector
Locationsin Wiring Diagrams for the location of
more information on the right headlamp and dash
wire harness retainer locations.
(5) Unlatch and open the PDC cover.
(6) Remove the two nuts that secure the two-holed
eyelet of the battery wire harness PDC take outs to
the PDC B(+) terminal studs (Fig. 8).
(7) Remove the battery wire harness PDC take out
eyelet from the B(+) terminal studs.
(8) Disengage the latches on the PDC housing
mounts from the tabs on the PDC mounting stan-
chions of the battery support, and pull the PDC
housing upward to disengage the mounts from the
stanchions (Fig. 9).
Fig. 8 Power Distribution Center Connections
1 - PDC COVER
2 - NUT (2)
3 - EYELET
4 - B(+) TERMINAL STUDS
Fig. 9 Power Distribution Center Remove/Install
1 - POWER DISTRIBUTION CENTER
2 - MOUNTS
3 - STANCHIONS (3)
4 - BATTERY SUPPORT
8W - 97 - 8 8W-97 POWER DISTRIBUTIONWJ
POWER DISTRIBUTION CENTER (Continued)

PDC LOWER COVER INSTALLATION
(1) Align the PDC housing lower cover on the bot-
tom of the PDC.
(2) Evenly press the lower cover into place until
latches are fully engaged.
(3) Where the right headlamp and dash harness
enters the PDC, tape the harness securely to the
trough formation on the PDC lower cover.
(4) Install the PDC in its mounting location on the
battery support.
(5) Install the battery wire harness over the two
PDC B+ terminal studs. Torque the nuts to 11.3 N´m
(100 in. lbs.).
(6) Install the battery. Refer to Battery System for
the procedure.
(7) Install the PDC cover.
INSTALLATION
The Power Distribution Center (PDC) main hous-
ing unit, the PDC fuse wedges and the PDC bus bars
cannot be repaired and are only serviced as a unit
with the right headlamp and dash wire harness. If
the PDC main housing unit, the fuse wedges or the
bus bars are faulty or damaged, the entire PDC and
right headlamp and dash wire harness unit must be
replaced.
(1) Position the PDC and the right headlamp and
dash wire harness unit in the engine compartment.
(2) Engage the PDC housing mounts with the
stanchions of the battery support and push the unit
downward until the mount latches fully engage the
mounting tabs on the stanchions.
(3) Install the two-holed eyelet of the battery wire
harness PDC take outs onto the two PDC B(+) termi-
nal studs.
(4) Install and tighten the nuts that secure the
eyelet of the battery wire harness PDC take outs to
the B(+) terminal studs. Tighten the nuts to 11.3
N´m (100 in. lbs.).
(5) Engage each of the retainers that secure the
right headlamp and dash wire harness to the vehicle
body and chassis components. Refer toConnector
Locationsin Wiring Diagrams for the location of
more information on the right headlamp and dash
wire harness retainer locations.
(6) Install all of the fasteners that secure each of
the right headlamp and dash wire harness ground
eyelets to the vehicle body and chassis components.
Refer toConnector Locationsin Wiring Diagrams
for the location of more information on the ground
eyelet locations.
(7) Reconnect each of the right headlamp and dash
wire harness connectors. Refer toConnector Loca-
tionsin Wiring Diagrams for the location of more
information on the right headlamp and dash wire
harness connector locations. For connectors securedwith screws, tighten the screws to 4.3 N´m (38 in.
lbs.).
(8) Reconnect the battery negative cable.
POWER OUTLET
DESCRIPTION - FRONT POWER OUTLET
An accessory power outlet is standard equipment
on this model. The power outlet is installed in the
instrument panel center lower bezel, which is located
near the bottom of the instrument panel center stack
area, below the heater and air conditioner controls.
The power outlet base is secured by a snap fit within
the center lower bezel. A hinged door with an over-
center spring flips closed to conceal and protect the
power outlet base when the power outlet is not being
used, and flips open below the center lower bezel
while the power outlet is in use.
The power outlet receptacle unit and the power
outlet door are each available for service replace-
ment.
OPERATION - FRONT POWER OUTLET
The power outlet base or receptacle shell is con-
nected to ground, and an insulated contact in the
bottom of the shell is connected to battery current.
The power outlet receives battery voltage from a fuse
in the junction block at all times.
While the power outlet is very similar to a cigar
lighter base unit, it does not include the two small
spring-clip retainers inside the bottom of the recepta-
cle shell that are used to secure the cigar lighter
heating element to the insulated contact.
DIAGNOSIS AND TESTING - POWER OUTLET
For complete circuit diagrams, refer toHorn/Ci-
gar Lighter/Power Outletin Wiring Diagrams.
WARNING: REFER TO RESTRAINTS BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. FAILURE TO TAKE THE
PROPER PRECAUTIONS COULD RESULT IN ACCI-
DENTAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
(1) Check the fused B(+) fuse in the junction block.
If OK, go to Step 2. If not OK, repair the shorted cir-
cuit or component as required and replace the faulty
fuse.
(2) Check for battery voltage at the fused B(+) fuse
in the junction block. If OK, go to Step 3. If not OK,
repair the open fused B(+) circuit to the Power Dis-
tribution Center (PDC) fuse as required.
(3) Open the power outlet door. Check for continu-
ity between the inside circumference of the power
8W - 97 - 12 8W-97 POWER DISTRIBUTIONWJ
POWER DISTRIBUTION CENTER (Continued)

outlet receptacle and a good ground. There should be
continuity. If OK, go to Step 4. If not OK, go to Step
5.
(4) Check for battery voltage at the insulated con-
tact located at the back of the power outlet recepta-
cle. If not OK, go to Step 5.
(5) Disconnect and isolate the battery negative
cable. Remove the instrument panel center lower
bezel. Check for continuity between the ground cir-
cuit cavity of the power outlet wire harness connector
and a good ground. There should be continuity. If
OK, go to Step 6. If not OK, repair the open ground
circuit to ground as required.
(6) Connect the battery negative cable. Check for
battery voltage at the fused B(+) circuit cavity of the
power outlet wire harness connector. If OK, replace
the faulty power outlet receptacle. If not OK, repair
the open fused B(+) circuit to the junction block fuse
as required.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the center lower bezel from the instru-
ment panel. Refer toInstrument Panel Center
Lower Bezelin Body for the procedure.
(3) Pull the cigar lighter knob and element or the
protective cap out of the cigar lighter receptacle base,
or open the power outlet door in the instrument
panel center lower bezel.
(4) Look inside the cigar lighter or power outlet
receptacle base and note the position of the rectangu-
lar retaining bosses of the mount that secures the
receptacle base to the instrument panel center lower
bezel (Fig. 15).
(5) Insert a pair of external snap ring pliers into
the cigar lighter or power outlet receptacle base and
engage the tips of the pliers with the retaining
bosses of the mount.
(6) Squeeze the pliers to disengage the mount
retaining bosses from the receptacle base and, using
a gentle rocking motion, pull the pliers and the
receptacle base out of the mount.
(7) Remove the cigar lighter or power outlet mount
from the instrument panel center lower bezel.
INSTALLATION
(1) Install the cigar lighter or power outlet mount
into the instrument panel center lower bezel.
(2) Align the splines on the outside of the cigar
lighter or power outlet receptacle base connector
receptacle with the grooves on the inside of the
mount.
(3) Press firmly on the cigar lighter or power out-
let receptacle base until the retaining bosses of the
mount are fully engaged in their receptacles.(4) Install the cigar lighter knob and element or
the protective cap into the cigar lighter receptacle
base, or close the power outlet door in the instrument
panel center lower bezel.
(5) Install the center lower bezel onto the instru-
ment panel. Refer toInstrument Panel Center
Lower Bezelin Body for the procedure.
(6) Reconnect the battery negative cable.
POWER OUTLET RELAY
DESCRIPTION
The power outlet / cigar lighter relay is an electro-
mechanical device that switches fused battery cur-
rent to the cigar lighter or power outlet when the
ignition switch is turned to the Accessory or On posi-
tions. The power outlet / cigar lighter relay is located
in the junction block, below the driver side of the
instrument panel in the passenger compartment.
The cigar lighter relay is a International Standards
Organization (ISO) relay. Relays conforming to the
ISO specifications have common physical dimensions,
current capacities, terminal patterns, and terminal
functions.
Fig. 15 Cigar Lighter and Power Outlet Remove/
Install - Typical
1 - KNOB AND ELEMENT
2 - RETAINING BOSSES-ENGAGE PLIERS HERE
3 - BASE
4 - PARTIALLY REMOVED
5 - EXTERNAL SNAP-RING PLIERS
6 - MOUNT
7 - BASE
WJ8W-97 POWER DISTRIBUTION 8W - 97 - 13
POWER OUTLET (Continued)

ground at all times. If not OK, repair the open
ground circuit to ground as required.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the steering column opening cover
from the instrument panel. Refer toSteering Col-
umn Opening Coverin Body for the procedure.
(3) The power outlet / cigar lighter relay is located
on the left side of the combination flasher in the
junction block.
(4) Remove the power outlet / cigar lighter relay
from the junction block.
INSTALLATION
(1) Position the power outlet / cigar lighter relay in
the proper receptacle in the junction block.
(2) Align the power outlet / cigar lighter relay ter-
minals with the terminal cavities in the junction
block receptacle.
(3) Push in firmly on the power outlet / cigar
lighter relay until the terminals are fully seated in
the terminal cavities in the junction block receptacle.
(4) Install the steering column opening cover onto
the instrument panel. Refer toSteering Column
Opening Coverin Body for the procedure.
(5) Reconnect the battery negative cable.
IOD WIRE HARNESS
CONNECTOR
DESCRIPTION
All vehicles are equipped with an Ignition-Off
Draw (IOD) connector that is located in a molded
connector receptacle on the lower rear surface of the
Junction Block (JB) housing (Fig. 17). The JB is con-
cealed above the molded plastic instrument panel
fuse cover. Integral latches molded into the fuse
cover secure it the JB, the Body Control Module
(BCM) and the 16-way data link connector tab of the
instrument panel steering column support bracket.
The fuse cover can be pulled downward to disengage
the latches and provide service access to all of the
fuses, relays and wire harness connectors of the JB.
Refer toInstrument Panel Fuse Coverin the
index of this service manual for the location of addi-
tional service information covering the fuse cover.
OPERATION
The term ignition-off draw identifies a normal con-
dition where power is being drained from the battery
with the ignition switch in the Off position. The IOD
connector feeds the memory and sleep mode func-
tions for some of the electronic modules in the vehicleas well as various other accessories that require bat-
tery current when the ignition switch is in the Off
position, including the clock.
The IOD connector can be used by the vehicle
owner as a convenient means of reducing battery
depletion when a vehicle is to be stored for periods
not to exceed about twenty days (short-term storage).
Simply disconnect the IOD connector from the JB
receptacle. However, it must be remembered that dis-
connecting the IOD connector will not eliminate IOD,
but only reduce this normal condition. When a vehi-
cle will not be used for more than twenty days, but
less than thirty days, remove the IOD fuse from the
Power Distribution Center (PDC). If a vehicle will be
stored for more than about thirty days, the battery
negative cable should be disconnected to eliminate
normal IOD; and, the battery should be tested and
recharged at regular intervals during the vehicle
storage period to prevent the battery from becoming
discharged or damaged. Refer toIgnition-Off Draw
Fig. 17 Ignition-Off Draw Connector
1 - SNAP CLIPS
2 - SCREW
3 - CONNECTOR
4 - LEFT BODY WIRE HARNESS
5 - IOD CONNECTOR
6 - FUSED B+ CONNECTOR
7 - RIGHT BODY WIRE HARNESS
8 - SCREW
9 - CONNECTOR
10 - JUNCTION BLOCK
WJ8W-97 POWER DISTRIBUTION 8W - 97 - 15
POWER OUTLET RELAY (Continued)

FuseandBatteryin the index in this service man-
ual for the location of additional service information
covering the ignition-off draw fuse and the battery.
FUSE COVER
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Pull down on the rear edge (nearest the rear of
the vehicle) of the instrument panel fuse cover until
the rear latches unsnap from the tabs on the lower
junction block housing and the side latch unsnaps
from the tab on the instrument panel steering col-
umn support bracket outboard of the 16-way data
link connector (Fig. 18).
(3) Move the instrument panel fuse cover towards
the front of the vehicle to disengage the front latches
from the mounting slots in the lower housing of the
body control module.
(4) Remove the fuse cover from under the instru-
ment panel.
INSTALLATION
(1) Position the two front latches of the instrument
panel fuse cover within the two locator channel for-
mations on the bottom of the body control module
housing (Fig. 19).
(2) While applying a slight upward pressure to the
instrument panel fuse cover over the front latches,
slowly slide the front latches through the locator
channels toward the front of the vehicle until thelatches exit the front of the locator channels. This
will locate the front latches at the mounting slots in
the lower housing of the body control module.
(3) Apply a slight rearward pressure on the instru-
ment panel fuse cover to engage the front latches in
the mounting slots in the lower housing of the body
control module.
(4) Swing the rear edge (nearest the rear of the
vehicle) of the instrument panel fuse cover up toward
the junction block.
(5) Press firmly upward on the instrument panel
fuse cover over the rear latches until the latches
snap into place over the tabs on the lower edge of the
junction block housing.
(6) Press firmly upward on the 16-way data link
connector cover formation of the instrument panel
fuse cover until the side latch snaps into place over
the tab on the outboard side of the instrument panel
steering column support bracket.
(7) Reconnect the battery negative cable.
REAR POWER OUTLET
DESCRIPTION - REAR POWER OUTLET
A rear accessory power outlet is optional equip-
ment on this model. The rear power outlet is
installed in the lower right quarter trim panel near
the right liftgate opening pillar in the cargo area of
Fig. 18 Instrument Panel Fuse Cover Remove/Install
1 - REAR LATCHES
2 - JUNCTION BLOCK AND BODY CONTROL MODULE UNIT
3 - INSTRUMENT PANEL FUSE COVER
4 - SIDE LATCH
5 - FRONT LATCHES
Fig. 19 Instrument Panel Fuse Cover Locator
Channels
1 - JUNCTION BLOCK
2 - SCREWS (4)
3 - BODY CONTROL MODULE
4 - FUSE COVER LOCATOR CHANNELS
5 - FUSE COVER MOUNTING SLOTS
6 - INSTRUMENT PANEL WIRE HARNESS CONNECTORS
8W - 97 - 16 8W-97 POWER DISTRIBUTIONWJ
IOD WIRE HARNESS CONNECTOR (Continued)

the vehicle. The power outlet base and mount are
secured by a snap fit within the quarter trim panel.
A plastic protective cap snaps into the power outlet
base when the power outlet is not being used, and
hangs from the power outlet base mount by an inte-
gral bail strap while the power outlet is in use. While
the power outlet is very similar to a cigar lighter
base unit, it does not include the two small spring-
clip retainers inside the bottom of the receptacle
shell that are used to secure the cigar lighter heating
element to the insulated contact.
The power outlet receptacle unit and the accessory
power outlet protective cap are available for service.
The power outlet receptacle cannot be repaired and,
if faulty or damaged, it must be replaced.
OPERATION - REAR POWER OUTLET
The power outlet base or receptacle shell is con-
nected to ground, and an insulated contact in the
bottom of the shell is connected to battery current.
The power outlet receives battery voltage from a fuse
in the Power Distribution Center (PDC) through a
fuse in the Junction Block (JB) at all times. Refer to
Horn/Cigar Lighter/Power Outletin Wiring Dia-
grams for the location of complete rear power outlet
circuit diagrams.
DIAGNOSIS AND TESTING - REAR POWER
OUTLET
Refer toHorn/Cigar Lighter/Power Outletin
Wiring Diagrams for the location of complete rear
power outlet circuit diagrams.
(1) Check the fused B(+) fuse in the Junction
Block (JB). If OK, go to Step 2. If not OK, repair the
shorted circuit or component as required and replace
the faulty fuse.
(2) Check for battery voltage at the fused B(+) fuse
in the JB. If OK, go to Step 3. If not OK, repair the
open fused B(+) circuit to the Power Distribution
Center (PDC) as required.
(3) Remove the plastic protective cap from the rear
power outlet receptacle. Check for continuity between
the inside circumference of the rear power outlet
receptacle and a good ground. There should be conti-
nuity. If OK, go to Step 4. If not OK, go to Step 5.
(4) Check for battery voltage at the insulated con-
tact located at the back of the rear power outlet
receptacle. If not OK, go to Step 5.(5) Disconnect and isolate the battery negative
cable. Remove the rear power outlet from the right
quarter trim panel. Check for continuity between the
ground circuit cavity of the rear power outlet wire
harness connector and a good ground. There should
be continuity. If OK, go to Step 6. If not OK, repair
the open ground circuit to ground as required.
(6) Connect the battery negative cable. Check for
battery voltage at the fused B(+) circuit cavity of the
rear power outlet wire harness connector. If OK,
replace the faulty rear power outlet receptacle base.
If not OK, repair the open fused B(+) circuit to the
JB fuse as required.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Pull the protective cap out of the rear power
outlet receptacle base (Fig. 20).
Fig. 20 Rear Power Outlet Remove/Install
1 - RIGHT QUARTER TRIM PANEL
2 - RIGHT BODY WIRE HARNESS CONNECTOR
3 - RECEPTACLE BASE
4 - PROTECTIVE CAP
5 - MOUNT
WJ8W-97 POWER DISTRIBUTION 8W - 97 - 17
REAR POWER OUTLET (Continued)

(3) Look inside the rear power outlet receptacle
base and note the position of the rectangular retain-
ing bosses of the mount that secures the receptacle
base to the right quarter trim panel (Fig. 21).(4) Insert a pair of external snap ring pliers into
the rear power outlet receptacle base and engage the
tips of the pliers with the retaining bosses of the
mount.
(5) Squeeze the pliers to disengage the mount
retaining bosses from the receptacle base and, using
a gentle rocking motion, pull the pliers and the
receptacle base out of the mount.
(6) Pull the rear power outlet receptacle base away
from the right quarter trim panel far enough to
access the wire harness connector.
(7) Disconnect the right body wire harness connec-
tor from the rear power outlet receptacle base con-
nector receptacle.
(8) Remove the rear power outlet mount from the
right quarter trim panel.
INSTALLATION
(1) Align the splines on the outside of the rear
power outlet receptacle base connector receptacle
with the grooves on the inside of the mount.
(2) Insert the rear power outlet receptacle base
about half way through the mount.
(3) Reconnect the right body wire harness connec-
tor to the rear power outlet receptacle base connector
receptacle.
(4) Insert the rear power outlet receptacle base
and mount into the right quarter trim panel as a
unit until the mount is seated flush against the trim
panel.
(5) Press firmly on the rear power outlet receptacle
base until the retaining bosses of the mount are fully
engaged in their receptacles.
(6) Install the protective cap into the rear power
outlet receptacle base.
(7) Reconnect the battery negative cable.
Fig. 21 Power Outlet Remove/Install - Typical
1 - KNOB AND ELEMENT
2 - RETAINING BOSSES-ENGAGE PLIERS HERE
3 - BASE
4 - PARTIALLY REMOVED
5 - EXTERNAL SNAP-RING PLIERS
6 - MOUNT
7 - BASE
8W - 97 - 18 8W-97 POWER DISTRIBUTIONWJ
REAR POWER OUTLET (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
3. Worn or incorrect gapped spark
plugs3. Clean plugs and set gap. (Refer to
8 - ELECTRICAL/IGNITION
CONTROL/SPARK PLUG -
CLEANING).
4. Dirt or water in fuel system 4. Clean system and replace fuel
filter
5. Faulty fuel pump 5. Install new fuel pump
6. Incorrect valve timing 6. Correct valve timing
7. Blown cylinder head gasket 7. Install new cylinder head gasket
8. Low compression 8. Test cylinder compression. (Refer
to 9 - ENGINE - DIAGNOSIS AND
TESTING).
9. Burned, warped, or pitted valves 9. Install/Reface valves as necessary
10. Plugged or restricted exhaust
system10. Install new parts as necessary
11. Faulty ignition coil rail 11. Test and replace, as necessary.
(Refer to 8 - ELECTRICAL/IGNITION
CONTROL/COIL RAIL - REMOVAL).
ENGINE STALLS OR ROUGH
IDLE1. Carbon build-up on throttle plate 1. Remove throttle body and
de-carbon. (Refer to 14 - FUEL
SYSTEM/FUEL INJECTION/
THROTTLE BODY - REMOVAL) for
correct procedure.
2. Engine idle speed too low 2. Check Idle Air Control circuit.
3. Worn or incorrectly gapped spark
plugs3. Replace or clean and re-gap spark
plugs. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING)
4. Faulty coil rail 4. Test and replace, if necessary.
(Refer to 8 - ELECTRICAL/IGNITION
CONTROL/COIL RAIL - REMOVAL)
5. Intake manifold vacuum leak 5. Inspect intake manifold gasket and
vacuum hoses. Replace if necessary.
(Refer to 9 - ENGINE/MANIFOLDS/
INTAKE MANIFOLD - DIAGNOSIS
AND TESTING).
ENGINE MISSES ON
ACCELERATION1. Worn or incorrectly gapped spark
plugs1. Replace spark plugs or clean and
set gap.
2. Spark plug cables defective or
crossed2. Replace spark plug cables.
3. Dirt in fuel system 3. Clean fuel system
4. Burned, warped or pitted valves 4. Install new valves
5. Faulty coil rail 5. Test and replace as necessary.
(Refer to 8 - ELECTRICAL/IGNITION
CONTROL/COIL RAIL - REMOVAL)
WJENGINE - 4.0L 9 - 5
ENGINE - 4.0L (Continued)

DIAGNOSIS AND TESTINGÐCYLINDER
COMPRESSION PRESSURE
The results of a cylinder compression pressure test
can be utilized to diagnose several engine malfunc-
tions.
Ensure the battery is completely charged and the
engine starter motor is in good operating condition.
Otherwise, the indicated compression pressures may
not be valid for diagnosis purposes.
(1) Clean the spark plug recesses with compressed
air.
(2) Remove the spark plugs (Refer to 8 - ELEC-
TRICAL/IGNITION CONTROL/SPARK PLUG -
REMOVAL).
(3) Secure the throttle in the wide-open position.
(4) Disconnect the ignition coil.
(5) Insert a compression pressure gauge and rotate
the engine with the engine starter motor for three
revolutions.
(6) Record the compression pressure on the third
revolution. Continue the test for the remaining cylin-
ders.
(Refer to 9 - ENGINE - SPECIFICATIONS) for the
correct engine compression pressures.
DIAGNOSIS AND TESTING - CYLINDER
COMBUSTION PRESSURE LEAKAGE
The combustion pressure leakage test provides an
accurate means for determining engine condition.
Combustion pressure leakage testing will detect:
²Exhaust and intake valve leaks (improper seat-
ing)
²Leaks between adjacent cylinders or into water
jacket²Any causes for combustion/compression pressure
loss
WARNING: DO NOT REMOVE THE RADIATOR CAP
WITH THE SYSTEM HOT AND UNDER PRESSURE.
SERIOUS BURNS FROM HOT COOLANT CAN
OCCUR.
Check the coolant level and fill as required. DO
NOT install the radiator cap.
Start and operate the engine until it attains nor-
mal operating temperature, then turn OFF the
engine.
Remove the spark plugs.
Remove the oil filler cap.
Remove the air cleaner.
Calibrate the tester according to the manufactur-
er's instructions. The shop air source for testing
should maintain 483 kPa (70 psi) minimum, 1,379
kPa (200 psi) maximum and 552 kPa (80 psi) recom-
mended.
Perform the test procedure on each cylinder accord-
ing to the tester manufacturer's instructions. While
testing, listen for pressurized air escaping through
the throttle body, tailpipe or oil filler cap opening.
Check for bubbles in the radiator coolant.
All gauge pressure indications should be equal,
with no more than 25% leakage.
FOR EXAMPLE:At 552 kPa (80 psi) input pres-
sure, a minimum of 414 kPa (60 psi) should be main-
tained in the cylinder CYLINDER COMBUSTION
PRESSURE LEAKAGE DIAGNOSIS CHART .
CYLINDER COMBUSTION PRESSURE LEAKAGE DIAGNOSIS CHART
CONDITION POSSIBLE CAUSE CORRECTION
AIR ESCAPES THROUGH
THROTTLE BODYIntake valve bent, burnt, or not
seated properlyInspect valve and valve seat.
Reface or replace, as necessary
AIR ESCAPES THROUGH
TAILPIPEExhaust valve bent, burnt, or not
seated properlyInspect valve and valve seat.
Reface or replace, as necessary
AIR ESCAPES THROUGH
RADIATORHead gasket leaking or cracked
cylinder head or blockRemove cylinder head and inspect.
Replace defective part
MORE THAN 50% LEAKAGE
FROM ADJACENT CYLINDERSHead gasket leaking or crack in
cylinder head or block between
adjacent cylindersRemove cylinder head and inspect.
Replace gasket, head, or block as
necessary
MORE THAN 25% LEAKAGE AND
AIR ESCAPES THROUGH OIL
FILLER CAP OPENING ONLYStuck or broken piston rings;
cracked piston; worn rings and/or
cylinder wallInspect for broken rings or piston.
Measure ring gap and cylinder
diameter, taper and out-of-round.
Replace defective part as necessary
9 - 8 ENGINE - 4.0LWJ
ENGINE - 4.0L (Continued)

(7) Remove the fan assembly from the water pump
(Refer to 7 - COOLING/ENGINE/RADIATOR FAN -
REMOVAL).
(8) Remove the fan shroud.
(9) Disconnect the transmission fluid cooler lines
(automatic transmission).
(10) Discharge the A/C system (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE).
(11) Remove the service valves and cap the com-
pressor ports.
(12) Remove the radiator or radiator/condenser (if
equipped with A/C).
(13) Disconnect the heater hoses at the engine
thermostat housing and water pump.
(14) Disconnect the accelerator cable, transmission
line pressure cable and speed control cable (if
equipped) from the throttle body.
(15) Remove cables from the bracket and secure
out of the way.
(16) Disconnect the body ground at the engine.
(17) Disconnect the following connectors and
secure their harness out of the way.
²Power steering pressure switch
²Coolant temperature sensor
²Six (6) fuel injector connectors
²Intake air temperature sensor
²Throttle position sensor
²Map sensor
²Crankshaft position sensor
²Oxygen sensor
²Camshaft position sensor
²Generator connector and B+ terminal wire
(18) Disconnect the coil rail electrical connections
and the oil pressure switch connector.
(19) Perform the fuel pressure release procedure
(Refer to 14 - FUEL SYSTEM/FUEL DELIVERY -
STANDARD PROCEDURE).
(20) Disconnect the fuel supply line at the injector
rail (Refer to 14 - FUEL SYSTEM/FUEL DELIVERY/
QUICK CONNECT FITTING - STANDARD PROCE-
DURE).
(21) Remove the fuel line bracket from the intake
manifold.
(22) Remove the air cleaner assembly (Fig. 5).
(23) Disconnect the hoses from the fittings at the
steering gear.
(24) Drain the pump reservoir.
(25) Cap the fittings on the hoses and steering
gear to prevent foreign objects from entering the sys-
tem.
(26) Raise and support the vehicle.
(27) Disconnect the wires from the engine starter
motor solenoid.(28) Remove the engine starter motor (Refer to 8 -
ELECTRICAL/STARTING/STARTER MOTOR -
REMOVAL).
(29) Disconnect the oxygen sensor from the
exhaust pipe.
(30) Disconnect the exhaust pipe from the mani-
fold.
(31) Remove the exhaust pipe support.
(32) Remove the bending brace (Refer to 9 -
ENGINE/ENGINE BLOCK/STRUCT SUPPORT -
REMOVAL).
(33) Remove the engine flywheel/converter housing
access cover.
(34) Mark the converter and drive plate location.
(35) Remove the converter-to-drive plate bolts.
(36) Remove the upper engine flywheel/converter
housing bolts and loosen the bottom bolts.
(37) Remove the engine mount cushion-to-engine
compartment bracket bolts.
(38) Lower the vehicle.
(39) Attach a lifting device to the engine.
(40) Raise the engine off the front supports.
(41) Place a support or floor jack under the con-
verter (or engine flywheel) housing.
(42) Remove the remaining converter (or engine
flywheel) housing bolts.
(43) Lift the engine out of the engine compart-
ment.
Fig. 5 Air Cleaner Assembly
1 - POWER STEERING PUMP
2 - AIR CLEANER ASSEMBLY
9 - 12 ENGINE - 4.0LWJ
ENGINE - 4.0L (Continued)