tire pressure JEEP XJ 1995 Service And Repair Manual

VEHICLE SAFETY CERTIFICATION LABEL
A vehicle safety certification label (Fig. 1) is at-
tached to every Jeep vehicle. The label certifies that
the vehicle conforms to all applicable Federal Motor
Vehicle Safety Standards. The label also lists:
²Gross vehicle weight rating (GVWR) and the gross
front and rear axle weight ratings (GAWR's) based on
a minimum tire rim size and a maximum cold tire
inflation pressure.
²Month and year of vehicle manufacture.
²Vehicle identification number (VIN).
²Type of vehicle.
²Month, day and hour (MDH) of final assembly.
The label is located on the driver-side door shut-
face.
VEHICLE IDENTIFICATION NUMBER (VIN) PLATE
The Vehicle Identification Number (VIN) plate islocated on the lower windshield fence near the left
A-pillar. The VIN contains 17 characters that provide
data concerning the vehicle. Refer to the VIN decod-
ing chart to determine the identification of a vehicle.
The Vehicle Identification Number is also imprinted
on the:
²Body Code Plate.
²Vehicle Safety Certification Label.
²Frame rail.
To protect the consumer from theft and possible
fraud the manufacturer is required to include a
Check Digit at the ninth position of the Vehicle Iden-
tification Number. The check digit is used by the
manufacturer and government agencies to verify the
authenticity of the vehicle and official documentation.
The formula to use the check digit is not released to
the general public.
VEHICLE CODE PLATE
A metal vehicle code plate is attached to the left
(driver) side of the dash panel in the engine compart-
ment (Fig. 2). There can be a maximum of seven rows
of vehicle information imprinted on the plate. The
information should be read from left to right, starting
with line 1 at the bottom of the plate up through line
7 (as applicable) at the top of the code plate.
Refer to the decoding chart to decode lines 1 up
through 3.
Lines 4 through 7 (if used) on the vehicle code plate
are imprinted on the plate (in sequence) according to
the following:
VEHICLE IDENTIFICATION NUMBER (VIN) DECODING
Fig. 1 Vehicle Safety Certification LabelÐTypical
4 INTRODUCTIONJ

MAINTENANCE SCHEDULES
INTRODUCTION
There are two maintenance schedules that show
proper service intervals for Jeep Cherokee and Jeep
Wrangler vehicles. Use the schedule that best de-
scribes the conditions the vehicle is operated under.
When mileage and time is listed, follow the interval
that occurs first.
ScheduleÐAlists all the scheduled maintenance
to be performed under normal operating conditions.
ScheduleÐBis a schedule for vehicles that are
usually operated under one or more of the following
conditions.
²Frequent short trip driving less than 5 miles (8
km).
²Frequent driving in dusty conditions.
²Trailer towing or heavy load hauling.
²Frequent long periods of engine idling.
²Sustained high speed operation.
²Desert operation.
²Frequent starting and stopping.
²Cold climate operation.
²Off road driving.
²Commercial service.
²Snow plow operation.
²More than half of vehicle operation occurs in
heavy city traffic during hot weather (above 90É F).
AT EACH STOP FOR GASOLINE
²Check engine oil level and add as required.
²Check windshield washer solvent and add as re-
quired.
ONCE A MONTH
²Check tire pressure and look for unusual tire wear
or damage.
²Check fluid levels of coolant reservoir, brake mas-
ter cylinder, power steering and transmission. Add
fluid as required.
²Check all lights and other electrical items for cor-
rect operation.
²Inspect battery and clean and tighten terminals as
required.
²Check rubber seals on each side of the radiator for
proper fit.
AT EACH OIL CHANGE
²Inspect exhaust system.
²Inspect brake hoses.
²Rotate the tires at each oil change interval shown
on ScheduleÐA: (7,500 Miles) or every other interval
shown on ScheduleÐB: (6,000 Miles).
²Check engine coolant level, hoses, and clamps.
²Lubricate 4x4 steering linkage.
²Lubricate propeller shaft universal joints and slip
spline, if equipped.After completion of off-road (4WD) operation, the
underside of the vehicle should be thoroughly in-
spected. Examine threaded fasteners for looseness.
HARSH SURFACE ENVIRONMENTS
After vehicle operation in a harsh surface environ-
ment, the following components should be inspected
and cleaned as soon as possible:
²Brake drums.
²Brake linings.
²Front wheel bearings (2WD vehicles only).
²Axle coupling joints.
This will prevent wear and/or unpredictable brake
action.
EMISSION CONTROL SYSTEM MAINTENANCE
The schedule emission maintenance listed inbold
typeon the following schedules, must be done at the
mileage specified to assure the continued proper
functioning of the emission control system. These,
and all other maintenance services included in this
manual, should be done to provide the best vehicle
performance and reliability. More frequent mainte-
nance may be needed for vehicles in severe operating
conditions such as dusty areas and very short trip
driving.
SCHEDULEÐA
7,500 MILES (12 000 KM) OR AT 6 MONTHS
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
15,000 MILES (24 000 KM) OR AT 12 MONTHS
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage.
22,500 MILES (36 000 KM) OR AT 18 MONTHS
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
²Inspect brake linings.
30,000 MILES (48 000 KM) OR AT 24 MONTHS
²Replace air cleaner element.
²Replace spark plugs.
²Adjust belt tension on non-automatic tensioning
drive belts.
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage.
²Drain and refill automatic transmission.
²Drain and refill transfer case.
0 - 4 LUBRICATION AND MAINTENANCEJ

(2) Note any indication of drum/rotor overheating,
wheel dragging or the vehicle pulling to one side
when the brakes are applied.
(3) Evaluate any performance complaints received
from the owner/operator.
(4) Repair the brake system as necessary. Refer to
Group, 5 Brakes for additional information and ser-
vice procedures.
TIRES
RECOMMENDED MAINTENANCE
The general condition of the tires and the inflation
pressures should be inspected at the same time the
engine oil is changed and the oil filter is replaced.
In addition, the tires/wheels should be rotated at
the intervals described in the Maintenance Schedules
section of this group.
INSPECTION
Inspect the tires for excessive wear, damage, etc.
Test the tires for the recommended inflation pres-sure. Refer to the tire inflation pressure decal located
on the inside of the glove box door, and also to Group
22, Tires And Wheels.
ROTATION
Refer to Group 22, Tires And Wheels for the recom-
mended method of tire/wheel rotation for a Jeep ve-
hicle.
BODY COMPONENTS
LUBRICATION REQUIREMENTS
All Jeep operating mechanisms and linkages
should be lubricated when necessary. The door
weatherstrip seals should be lubricated to prolong
their life as well as to improve door sealing.
LUBRICANT SPECIFICATIONS
All applicable exterior and interior vehicle operat-
ing mechanisms should be:
²Inspected
²Cleaned
²Pivot/sliding contact areas on the mechanisms
should then be lubricated.
Multi-purpose NLGI GC-LB MOPAR Multi-Mileage
Lubricant or an equivalent, should be used to lubri-
cate the mechanisms. The door weatherstrip seals
should be lubricated with silicone lubricant spray.
Refer to the Body Lubricant Specifications chart be-
low for additional lubricant applications.
LUBRICATION
All pivoting and sliding contact areas, should be lu-
bricated periodically to ensure quiet, easy operation
and to protect against wear and corrosion. Areas in-
clude:
²Seat tracks.
²Door hinges/latches/strikers.
²Liftgate/tailgate/hood hinges (Fig. 11).
(1) As required, lubricate the body components
with the specified lubricants.
(2) Apply silicone lubricant to a cloth and wipe it
on door seals to avoid over-spray that can soil pas-
senger clothing.
(3) Before applying lubricant, the component
should be wiped clean. After lubrication, any excess
lubricant should be removed.
(4) The door lock cylinders should be lubricated 2
times each year (preferably autumn and spring):
²Spray a small amount of lock cylinder lubricant di-
rectly into the lock cylinder.
²Apply a small amount to the key and insert it into
the lock cylinder.
²Rotate it to the locked position and then back to
the unlocked position several times.
²Remove the key. Wipe the lubricant from it with a
clean cloth to avoid soiling of clothing.
Fig. 9 Park Brake Equalizer (XJ)ÐTypical
Fig. 10 Park Brake Equalizer (YJ)ÐTypical
0 - 32 LUBRICATION AND MAINTENANCEJ

even tire wear. The wheel toe position is thefinal
front wheel alignment adjustment.
²STEERING AXIS INCLINATION ANGLE is mea-
sured in degrees and is the angle that the steering
knuckles are tilted (Fig. 1). The inclination angle has
a fixed relationship with the camber angle. It will not
change except when a spindle or ball stud is dam-
aged or bent. The angle is not adjustable, the dam-
aged component(s) must be replaced to correct mis-
alignment.
WARNING: DO NOT ATTEMPT TO MODIFY ANY
SUSPENSION OR STEERING COMPONENT BY
HEATING AND BENDING.
PRE-ALIGNMENT INSPECTION
Before starting a front wheel alignment, the follow-
ing inspection and necessary corrections must be
completed.(1) Tires with the same recommended air pressure,
size, and thread wear. Refer to Group 22, Tires And
Wheels for diagnosis information.
(2) Front wheel bearings for wear and looseness.
(3) Ball studs, steering linkage pivot points and
steering gear for looseness, roughness, binding or
wear. Refer to Group 19, Steering for additional in-
formation.
(4) Front wheels for excessive radial or lateral
runout and unbalance. Refer to Group 22, Tires And
Wheels for diagnosis information.
(5) Suspension components for wear. Check compo-
nents for correct torque. Refer to Groups 2 and 3,
Suspension and Axle for additional information.
2 - 6 FRONT SUSPENSION AND AXLEJ

ABS BRAKE DIAGNOSIS
INDEX
page page
ABS Diagnostic Connector................... 3
ABS Warning Light Display................... 3
Antilock ECU and Hcu Diagnosis............... 3
DRB Scan Tool............................ 3General Information........................ 3
Normal Operating Conditions.................. 3
Wheel/Tire Size and Input Signals.............. 3
GENERAL INFORMATION
The DRB scan tool is required for ABS diagnosis.
The scan tool is used to identify ABS circuit faults.
Once a faulty circuit has been identified, refer to
the appropriate chassis/body diagnostic manual for
individual component testing.
ABS WARNING LIGHT DISPLAY
The amber antilock light illuminates at startup as
part of the system self check feature. The light illu-
minates for 2-3 seconds then goes off as part of the
normal check routine.
An ABS circuit fault is indicated when the amber
light remains on after startup, or illuminates during
vehicle operation.
Verify that a fault is actually related to the ABS
system before making repairs. For example, if the
red warning illuminates but the ABS light does not,
the problem is related to a service brake component
and not the ABS system. Or, if neither light illumi-
nates but a brake problem is noted, again, the prob-
lem is with a service brake component and not with
the ABS system.
ABS DIAGNOSTIC CONNECTOR
The ABS diagnostic connector is inside the vehicle.
The connector is the access point for the DRB scan tool.
On XJ models, the connector is located under the
instrument panel to the right of the steering column.
On some models, the connecter may be tucked under
the carpeting on the transmission tunnel. The con-
necter is a black, 6-way type.
On YJ models, the connector is under the instru-
ment panel by the the driver side kick panel. The
connecter is a black, 6 or 8-way type.
The DRB scan tool kit contains adapter cords for
both types of connecter. Use the appropriate cord for
test hookup.
DRB SCAN TOOL
ABS diagnosis is performed with the DRB scan tool.
Refer to the DRB scan tool manual for test hookup and
procedures. Diagnosis information is provided in the ap-
propriate chassis/body diagnostic manual.
WHEEL/TIRE SIZE AND INPUT SIGNALS
Antilock system operation is dependant on accurate
signals from the wheel speed sensors. Ideally, the ve-
hicle wheels and tires should all be the same size
and type. However, the Jeep ABS system is designed
to operate with a compact spare tire installed.
NORMAL OPERATING CONDITIONS
Sound Levels
The hydraulic control unit pump and solenoid valves
may produce some sound as they cycle on and off. This
is a normal condition and should not be mistaken for
faulty operation. Under most conditions, pump and so-
lenoid valve operating sounds will not be audible.
Vehicle Response In Antilock Mode
During antilock braking, the hydraulic control unit
solenoid valves cycle rapidly in response to antilock
electronic control unit signals.
The driver will experience a pulsing sensation
within the vehicle as the solenoids decrease, hold, or
increase pressure as needed. Brake pedal pulsing will
also be noted and is anormal condition.
Steering Response
A modest amount of steering input is required dur-
ing extremely high deceleration braking, or when
braking on differing traction surfaces. An example of
differing traction surfaces would be when the left
side wheels are on ice and the right side wheels are
on dry pavement.
Owner Induced Faults
Driving away with the parking brakes still applied
will cause warning light illumination. Pumping the
brake pedal will also generate a system fault and in-
terfere with ABS system operation.
ANTILOCK ECU AND HCU DIAGNOSIS
An ECU or HCU fault can only be determined
through testing with the DRB scan tool. Do not re-
place either component unless a fault is actually in-
dicated.
JABS BRAKE DIAGNOSIS 5 - 3

hand lever. Also note if vehicle was being operated
with parking brake partially applied (this will cause
red light to remain on).
(7) Check brake pedal operation. Verify that pedal
does not bind and has adequate free play. If pedal
lacks free play, check pedal and power booster for be-
ing loose or for bind condition. Do not road test until
condition is corrected.
(8) If components inspected look OK, road test ve-
hicle.
ROAD TESTING
(1) If amber warning light is on, problem is with
antilock system component. Refer to antilock diagno-
sis section.
(2) If red warning light is not on, proceed to step
(4).
(3) If red warning light is on, proceed as follows:
(a) See if parking brakes are applied. If brakes
are applied, release them and proceed to step (4).
(b) Note if brake pedal is abnormally low. If
pedal is definitely low and red light is still on,
check front/rear hydraulic circuits for leak.Do not
road test. Inspect and repair as needed.
(4) Check brake pedal response with transmission
in Neutral and engine running. Pedal should remain
firm under steady foot pressure. If pedal falls away,
do not road test as problem is in master cylinder, or
HCU on ABS models. If pedal holds firm, proceed to
next step.
(5) During road test, make normal and firm brake
stops in 25-35 mph range. Note faulty brake opera-
tion such as hard pedal, pull, grab, drag, noise, fade,
etc.
(6) Return to shop and inspect brake components.
Refer to inspection and diagnosis information.
COMPONENT INSPECTION
Fluid leak points and dragging brake units can
usually be located without removing any components.
The area around a leak point will be wet with fluid.
The components at a dragging brake unit (wheel,
tire, rotor) will be quite warm or hot to the touch.
Other brake problem conditions will require compo-
nent removal for proper inspection. Raise the vehicle
and remove the necessary wheels for better visual ac-
cess.
During component inspection, pay particular atten-
tion to heavily rusted/corroded brake components
(e.g. rotors, caliper pistons, brake return/holddown
springs, support plates, etc.).
Heavy accumulations of rust may be covering se-
vere damage to a brake component. It is wise to re-
move surface rust in order to accurately determine
the depth of rust penetration and damage. Light sur-
face rust is fairly normal and not a major concern (as
long as it is removed). However, heavy rust buildup,especially on high mileage vehicles may cover struc-
tural damage to such important components as
brakelines, rotors, support plates, and brake boost-
ers. Refer to the wheel brake service procedures in
this group for more information.
BRAKE WARNING LIGHT OPERATION
The red brake warning light will illuminate under
the following conditions:
²for 2-3 seconds at startup as part of normal bulb
check
²when parking brakes are applied
²low pedal caused by leak in front/rear brake hy-
draulic circuit
If the red light remains on after startup, first ver-
ify that the parking brakes are fully released. Then
check pedal action and fluid level. A red light plus
low pedal indicates the pressure differential switch
and valve have been actuated due to a system leak.
On models with ABS brakes, the amber warning
light only illuminates when an ABS malfunction has
occurred. The ABS light operates independently of
the red warning light.
PEDAL FALLS AWAY
A brake pedal that falls away under steady foot
pressure is generally the result of a system leak. The
leak point could be at a brakeline, fitting, hose,
wheel cylinder, or caliper. Internal leakage in the
master cylinder caused by worn or damaged piston
cups, may also be the problem cause.
If leakage is severe, fluid will be evident at or
around the leaking component. However internal
leakage in the master cylinder will not be physically
evident. Refer to the cylinder test procedure at the
end of this section.
LOW PEDAL
If a low pedal is experienced, pump the pedal sev-
eral times. If the pedal comes back up, worn lining
and worn rotors or drums are the most likely causes.
However, if the pedal remains low and the red warn-
ing light is on, the likely cause is a leak in the hy-
draulic system.
A decrease in master cylinder fluid level may only
be the result of normal lining wear. Fluid level will
drop somewhat as lining wear occurs. It is a result of
the outward movement of caliper and wheel cylinder
pistons to compensate for normal wear.
SPONGY PEDAL
Air in the system is the usual cause of a spongy
pedal. Brake drums machined way beyond allowable
limits (too thin), or substandard brake lines and
hoses can also cause a condition similar to a spongy
JSERVICE BRAKE DIAGNOSIS 5 - 5

produce a condition similar to grab as the tire loses
and recovers traction.
Flat-spotted tires can cause vibration and wheel
tramp and generate shudder during brake operation.
A tire with internal damage such as a severe bruise
or ply separation can cause vibration and pull. The
pull will be magnified when braking.
DIAGNOSING PARKING BRAKE MALFUNCTIONS
Adjustment Mechanism
Parking brake adjustment is controlled by a ca-
ble tensioner mechanism. The cable tensioner,
once adjusted at the factory, will not need further
attention under normal circumstances. There are
only two instances when adjustment is required.
The first is when a new tensioner, or cables have
been installed. And the second, is when the ten-
sioner and cables are disconnected for access to
other brake components.
Parking Brake Switch And Warning Light Illumination
The parking brake switch on the lever, or foot
pedal, is in circuit with the red warning light. The
switch will illuminate the red light only when the
parking brakes are applied. If the light remains on
after parking brake release, the switch or wires are
faulty, or cable tensioner adjustment is incorrect.
If the red light comes on while the vehicle is in mo-
tion and brake pedal height decreases, a fault has oc-
curred in the front or rear brake hydraulic system.
Parking Brake problem Causes
In most cases, the actual cause of an improperly
functioning parking brake (too loose/too tight/wont
hold), can be traced to a drum brake component.
The leading cause of improper parking brake
operation, is excessive clearance between the
brakeshoes and the drum surface. Excessive
clearance is a result of: lining and/or drum
wear; oversize drums; or inoperative shoe ad-
juster components.
Excessive parking brake lever travel (sometimes de-
scribed as a loose lever or too loose condition), is the re-
sult of worn brakeshoes/drums, improper brakeshoe
adjustment, or incorrectly assembled brake parts.
A ``too loose'' condition can also be caused by inop-
erative brakeshoe adjusters. If the adjusters are mis-
assembled, they will not function. In addition, since
the adjuster mechanism only works during reverse
stops, it is important that complete stops be made.
The adjuster mechanism does not operate when roll-
ing stops are made in reverse. The vehicle must be
brought to a complete halt before the adjuster lever
will turn the adjuster screw.
A condition where the parking brakes do not hold, will
most probably be due to a wheel brake component.
Items to look for when diagnosing a parking brake
problem, are:
²rear brakeshoe wear or adjuster problem
²rear brake drum wear
²brake drums machined beyond allowable diameter
(oversize)
²parking brake front cable not secured to lever
²parking brake rear cable seized
²parking brake strut reversed
²parking brake strut not seated in both shoes
²parking brake lever not seated in secondary shoe
²parking brake lever or brakeshoe bind on support
plate
²brakeshoes reversed
²adjuster screws seized
²adjuster screws reversed
²holddown or return springs misassembled or lack
tension
²wheel cylinder pistons seized
Brake drums that are machined oversize are diffi-
cult to identify without inspection. If oversize drums
are suspected, diameter of the braking surface will
have to be checked with an accurate drum gauge.
Oversize drums will cause low brake pedal and lack
of parking brake holding ability.
Improper parking brake strut and lever installation
will result in unsatisfactory parking brake operation.
Intermixing the adjuster screws will cause drag, bind
and pull along with poor parking brake operation.
Parking brake adjustment and parts replacement pro-
cedures are described in the Parking Brake section.
MASTER CYLINDER/POWER BOOSTER TEST
(1) Start engine and check booster vacuum hose
connections. Hissing noise indicates vacuum leak.
Correct any vacuum leak before proceeding.
(2) Stop engine and shift transmission into Neu-
tral.
(3) Pump brake pedal until all vacuum reserve in
booster is depleted.
(4) Press and hold brake pedal under light foot
pressure.
(a) If pedal holds firm, proceed to step (5).
(b) If pedal does not hold firm and falls away,
master cylinder is faulty due to internal leakage.
Overhaul or replace cylinder.
(5) Start engine and note pedal action.
(a) If pedal falls away slightly under light foot
pressure then holds firm, proceed to step (6).
(b) If no pedal action is discernible, or hard pedal
is noted, power booster or vacuum check valve is
faulty. Install known good check valve and repeat
steps (2) through (5).
(6) Rebuild booster vacuum reserve as follows: Re-
lease brake pedal. Increase engine speed to 1500
rpm, close throttle and immediately turn off ignition.
5 - 8 SERVICE BRAKE DIAGNOSISJ

CAUTION: Be certain that battery cables are con-
nected to the correct battery terminals. Reverse po-
larity can damage electrical components.
(12) Place oiled felt washer on battery positive ter-
minal post.
(13) Install and tighten battery positive cable ter-
minal clamp. Then install and tighten negative cableterminal clamp. Both cable clamp bolts require
torque of 8.5 Nzm (75 in. lbs.).
(14) Apply a thin coating of petroleum jelly or
chassis grease to cable terminals and battery posts.
STARTER AND STARTER RELAY
GENERAL INFORMATION
This section covers starter and starter relay service
procedures only. For diagnostic procedures, refer to
Group 8A - Battery/Starting/Charging Systems Diag-
nostics. Service procedures for other starting system
components can be found as follows:
²battery - see Battery, in this group
²ignition switch - refer to Group 8D - Ignition Sys-
tems
²park/neutral position switch (automatic transmis-
sion) - refer to Group 21 - Transmission and Transfer
Case
²wiring harness and connectors - refer to Group 8W
- Wiring Diagrams.
STARTER
The starter motor incorporates several features to
create a reliable, efficient, compact and lightweight
unit. A planetary gear system (intermediate trans-
mission) is used between the electric motor and pin-
ion gear. This feature makes it possible to reduce the
dimensions of the starter. At the same time, it allows
higher armature rotational speed and delivers in-
creased torque through the pinion gear to the fly-
wheel or drive plate ring gear.
The use of a permanent magnet field also reduces
starter size and weight. This field consists of six
high-strength permanent magnets. The magnets are
aligned according to their polarity and are perma-
nently fixed in the starter field frame.
The starter motors for all engines are activated by
a solenoid mounted to the overrunning clutch hous-
ing. However, the starter motor/solenoid are serviced
only as a complete assembly. If either component
fails, the entire assembly must be replaced.
This unit is highly sensitive to hammering, shocks
and external pressure.
CAUTION: The starter motor MUST NOT BE
CLAMPED in a vise by the starter field frame. Doing
so may damage the magnets. It may be clamped by
the mounting flange ONLY.CAUTION: Do not connect starter motor incorrectly
when tests are being performed. The permanent
magnets may be damaged and rendered unservice-
able.
STARTER RELAY
The starter relay is an International Standards Or-
ganization (ISO) type relay, and is located in the
Power Distribution Center (PDC). Refer to underside
of PDC cover for relay location.
STARTER REMOVE/INSTALLÐ2.5L
XJ MODELS
(1) Disconnect battery negative cable.
(2) Remove exhaust clamp from bracket (Fig. 11).
(3) Remove nut and bolt from forward end of brace
rod (automatic transmission only).
Fig. 11 Exhaust Clamp and Brace Remove (XJÐ
2.5L)
8B - 4 BATTERY/STARTER/GENERATOR SERVICEJ

(4) Crank the engine for 5 seconds while monitor-
ing the voltage at the coil positive terminal:
²If the voltage remains near zero during the entire
period of cranking, refer to On-Board Diagnostics in
Group 14, Fuel Systems. Check the powertrain con-
trol module (PCM) and auto shutdown relay.
²If voltage is at or near battery voltage and drops
to zero after 1-2 seconds of cranking, check the cam-
shaft position sensor-to-PCM circuit. Refer to On-
Board Diagnostics in Group 14, Fuel Systems.
²If voltage remains at or near battery voltage dur-
ing the entire 5 seconds, turn the key off. Remove
the 60-way connector (Fig. 15) from the PCM. Check
60-way connector for any spread terminals.
(5) Remove test lead from the coil positive termi-
nal. Connect an 18 gauge jumper wire between the
battery positive terminal and the coil positive termi-
nal.
(6) Make the special jumper shown in figure 16.
Using the jumper,momentarilyground pin/cavity
number 19 of the PCM 60-way connector. A spark
should be generated at the coil cable when the
ground is removed.
(7) If spark is generated, replace the powertrain
control module (PCM).
(8) If spark is not seen, use the special jumper to
ground the coil negative terminal directly.
(9) If spark is produced, repair wiring harness for
an open condition.
(10) If spark is not produced, replace the ignition
coil.IGNITION TIMING
Base (initial) ignition timing is NOT adjust-
able on any of the 2.5L 4-cylinder or 4.0L 6-cyl-
inder engines. Do not attempt to adjust ignition
timing by rotating the distributor.
Do not attempt to modify the distributor
housing to get distributor rotation. Distributor
position will have no effect on ignition timing.
All ignition timing functions are controlled by the
powertrain control module (PCM). Refer to On-Board
Diagnostics in the Multi-Port Fuel InjectionÐGen-
eral Diagnosis section of Group 14, Fuel Systems for
more information. Also refer to the appropriate Pow-
ertrain Diagnostics Procedures service manual for op-
eration of the DRB Scan Tool.
INTAKE MANIFOLD AIR TEMPERATURE SENSOR
TEST
For an operational description, diagnosis or remov-
al/ installation procedures, refer to Group 14, Fuel
Systems.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
TEST
For an operational description, diagnosis and re-
moval/installation procedures, refer to Group 14,
Fuel System.
POWERTRAIN CONTROL MODULE (PCM)
The PCM (formerly referred to as the SBEC or en-
gine controller) is located in the engine compartment
behind the windshield washer fluid tank on YJ mod-
els (Fig. 17). It is located in the engine compartment
next to the air cleaner on XJ models (Fig. 18).
The ignition system is controlled by the PCM.
For removal and installation of this component, re-
fer to the Component Removal/Installation section of
this group.
Fig. 15 PCM 60-Way Connector
Fig. 16 Special Jumper Ground-to-Coil Negative
Terminal
Fig. 17 PCM LocationÐYJ Models
JIGNITION SYSTEMS 8D - 11

The high-line cluster includes the following gauges:
²coolant temperature gauge
²fuel gauge
²oil pressure gauge
²speedometer/odometer
²tachometer
²trip odometer
²voltmeter.
The high-line cluster includes provisions for the fol-
lowing indicator lamps:
²anti-lock brake system lamp
²brake warning lamp
²four-wheel drive indicator lamps
²headlamp high beam indicator lamp
²low fuel warning lamp
²low washer fluid warning lamp
²malfunction indicator (Check Engine) lamp
²seat belt reminder lamp
²turn signal indicator lamps
²upshift indicator lamp.
GAUGES
With the ignition switch in the ON or START posi-
tion, voltage is supplied to all gauges through the in-
strument cluster gauge area printed circuit. With the
ignition switch in the OFF position, voltage is not
supplied to the gauges. A gauge pointer may remain
within the gauge scale after the ignition switch is
OFF. However, the gauges do not accurately indicate
any vehicle condition unless the ignition switch is
ON.
All gauges except the odometer are air core mag-
netic units. Two fixed electromagnetic coils are lo-
cated within the gauge. These coils are wrapped at
right angles to each other around a movable perma-
nent magnet. The movable magnet is suspended
within the coils on one end of a shaft. The gauge nee-
dle is attached to the other end of the shaft.
One of the coils has a fixed current flowing through
it to maintain a constant magnetic field strength.
Current flow through the second coil changes, which
causes changes in its magnetic field strength. The
current flowing through the second coil can be
changed by:
²a variable resistor-type sending unit (fuel level,
coolant temperature, or oil pressure)
²changes in electrical system voltage (voltmeter)
²electronic control circuitry (speedometer/odometer,
tachometer).
The gauge needle moves as the movable permanent
magnet aligns itself to the changing magnetic fields
created around it by the electromagnets.
COOLANT TEMPERATURE GAUGE
The coolant temperature gauge gives an indication
of engine coolant temperature. The coolant tempera-
ture sending unit is a thermistor that changes elec-
trical resistance with changes in engine coolanttemperature. High sending unit resistance causes
low coolant temperature readings. Low resistance
causes high coolant temperature readings.
The gauge will read at the high end of the scale
when the ignition switch is turned to the START po-
sition. This is caused by the bulb test circuit wiring
provision. The same wiring is used for the high-line
cluster with a coolant temperature gauge and the
low-line cluster with a coolant temperature warning
lamp. Sending unit resistance values are shown in a
chart in Specifications.
FUEL GAUGE
The fuel gauge gives an indication of the level of
fuel in the fuel tank. The fuel gauge sending unit has
a float attached to a swing-arm in the fuel tank. The
float moves up or down within the fuel tank as fuel
level changes. As the float moves, an electrical con-
tact on the swing-arm wipes across a resistor coil,
which changes sending unit resistance. High sending
unit resistance causes low fuel level readings. Low
resistance causes high fuel level readings. Sending
unit resistance values are shown in a chart in Spec-
ifications.
OIL PRESSURE GAUGE
The oil pressure gauge gives an indication of en-
gine oil pressure. The combination oil pressure send-
ing unit contains a flexible diaphragm. The
diaphragm moves in response to changes in engine
oil pressure. As the diaphragm moves, sending unit
resistance increases or decreases. High resistance on
the gauge side of the sending unit causes high oil
pressure readings. Low resistance causes low oil
pressure readings. Sending unit resistance values are
shown in a chart in Specifications.
SPEEDOMETER/ODOMETER
The speedometer/odometer gives an indication of
vehicle speed and travel distance. The speedometer
receives a vehicle speed pulse signal from the Vehicle
Speed Sensor (VSS). An electronic integrated circuit
contained within the speedometer reads and analyzes
the pulse signal. It then adjusts the ground path re-
sistance of one electromagnet in the gauge to control
needle movement. It also sends signals to an electric
stepper motor to control movement of the odometer
number rolls. Frequency values for the pulse signal
are shown in a chart in Specifications.
The VSS is mounted to an adapter near the trans-
mission (two-wheel drive) or transfer case (four-wheel
drive) output shaft. The sensor is driven through the
adapter by a speedometer pinion gear. The adapter
and pinion vary with transmission, transfer case,
axle ratio and tire size. Refer to Group 21 - Trans-
mission and Transfer Case for more information.
8E - 2 INSTRUMENT PANEL AND GAUGESÐXJJ