fuel type JEEP XJ 1995 Service And Repair Manual

FLUID CAPACITIES
Fuel Tank
XJ .....................................................76.4 L (20.2 gal.)
YJ(Standard) ......................................56.8 L (15 gal.)
YJ(Optional) .......................................75.7 L (20 gal.)
Engine Oil
2.5L ......................................................3.8 L (4.0 qts.)
4.0L ......................................................5.7 L (6.0 qts.)
Cooling System
2.5L(XJ).............................................9.5 L* (10 qts.*)
2.5L(YJ) ........................................8.5 L** (9.0 qts.**)
4.0L(XJ) ........................................11.4 L* (12.0 qts.*)
4.0L(YJ) ......................................9.9 L** (10.5 qts.**)
* Includes (2.2 L) (2.3 qts) for coolant recovery res-
ervoir.
** Includes (0.9 L) (1.0 qt.) for coolant recovery res-
ervoir.
Automatic Transmission
Dry fill capacity.*
AW4 (XJ-4.0L) ...................................8.0 L (16.9 pts.)
30RH (YJ-2.5L) .................................8.2 L (17.5 pts.)
32RH (YJ-4.0L) .................................8.2 L (17.5 pts.)
*Depending on type and size of internal cooler,
length and inside diameter of cooler lines, or use ofan auxiliary cooler, these figures may vary. Refer to
Group 21, Transmission for proper fluid fill proce-
dure.
Manual Transmission
AX4/5 (4X2) .........................................3.3 L (3.5 qts.)
AX5 (4X4) ............................................3.2 L (3.3 qts.)
AX15 (4X2) ..........................................3.1 L (3.2 qts.)
AX15 (4X4) ......................................3.15 L (3.32 qts.)
Fill to bottom of fill hole.
Transfer Case
SELEC-TRAC 242(XJ) .......................1.4 L (3.0 pts.)
COMMAND-TRAC 231(XJ) ...............1.0 L (2.2 pts.)
COMMAND-TRAC 231(YJ-Man Trans) ..1.5 L (3.25
pts.)
COMMAND-TRAC 231(YJ-Auto Trans) ....1.0 L (2.2
pts.)
Front Axle
MODEL 30 (YJ) ..............................1.65 L (3.76 pts.)
MODEL 30 (XJ) ..............................1.48 L (3.13 pts.)
Rear Axle
MODEL 35 (XJ-YJ) ........................1.6 L (3.38 pts.*)
8-1/4 (XJ) .........................................2.08 L (4.4 pts.*)
* When equipped with TRAC-LOK, include 2
ounces of Friction Modifier Additive.
JLUBRICATION AND MAINTENANCE 0 - 3

120,000 MILES (192 000KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage.
²Replace spark plugs.
²Drain and refill automatic transmission fluid.
²Change front and rear axle fluid.*
²Inspect brake linings.
²Replace air cleaner element.
²Replace distributor cap and rotor.
²Replace ignition wires.
²Adjust or replace drive belts.
²Replace fuel filter. See note #1.²Drain and refill transfer case fluid.
NOTE 1:Not required for California vehicles, rec-
ommended for proper vehicle performance.
* Off-highway operation, trailer towing, taxi, limou-
sine, bus, snow plowing, or other types of commercial
service or prolonged operation with heavy loading,
especially in hot weather, require front and rear axle
service indicated witha*inScheduleÐB. Perform
these services if you usually operate your vehicle un-
der these conditions.
Inspection and service should also be performed
anytime a malfunction is observed or suspected.
0 - 8 LUBRICATION AND MAINTENANCEJ

CAUTION: Do not crank starter motor on disabled
vehicle for more than 15 seconds, starter will over-
heat and could fail.
(6) Allow battery in disabled vehicle to charge to at
least 12.4 volts (75%charge) before attempting to
start engine. If engine does not start within 15 sec-
onds, stop cranking engine and allow starter to cool
(15 min.), before cranking again.
DISCONNECT CABLE CLAMPS AS FOLLOWS:
²Disconnect BLACK cable clamp from engine
ground on disabled vehicle.
²When using a Booster vehicle, disconnect BLACK
cable clamp from battery negative terminal. Discon-
nect RED cable clamp from battery positive terminal.
²Disconnect RED cable clamp from battery positive
terminal on disabled vehicle.
PORTABLE STARTING UNIT
There are many types of portable starting units
available for starting engines. Follow the manufac-
turer's instructions and observe the listed precau-
tions when involved in any engine starting
procedure.
HOISTING RECOMMENDATIONS
Refer to the Owner's Manual for emergency vehicle
lifting procedures.
FLOOR JACK
When properly positioned, a floor jack can be used
to lift a Jeep vehicle (Fig. 2 and 3). Support the ve-
hicle in the raised position with jack stands at the
front and rear ends of the frame rails.
CAUTION: Do not attempt to lift a Jeep vehicle with
a floor jack positioned under:
²An axle tube.
²A body side sill.
²A steering linkage component.
²A drive shaft.
²The engine or transmission oil pan.
²The fuel tank.
²A front suspension arm.
Use the correct sub-frame rail or frame rail
lifting locations only (Fig. 2 and 3).
HOIST
A vehicle can be lifted with:
²A single-post, frame-contact hoist.
²A twin-post, chassis hoist.
²A ramp-type, drive-on hoist.
When a frame-contact type hoist is used, ver-
ify that the lifting pads are positioned properly
(Fig. 2 and 3).WARNING: THE HOISTING AND JACK LIFTING
POINTS PROVIDED ARE FOR A COMPLETE VEHI-
CLE. WHEN A CHASSIS OR DRIVETRAIN COMPO-
NENT IS REMOVED FROM A VEHICLE, THE
CENTER OF GRAVITY IS ALTERED MAKING SOME
HOISTING CONDITIONS UNSTABLE. PROPERLY
SUPPORT OR SECURE VEHICLE TO HOISTING DE-
VICE WHEN THESE CONDITIONS EXIST.
TOWING RECOMMENDATIONS
A vehicle equipped with SAE approved sling-type
towing equipment can be used to tow all Jeep vehi-
cles. When towing a 4WD vehicle using a wheel-lift
towing device, use a tow dolly under the opposite end
of the vehicle. A vehicle with flat-bed device can also
be used to transport a disabled vehicle (Fig. 4).
A wooden crossbeam may be required for proper
connection when using the sling-type, front-end tow-
ing method.
SAFETY PRECAUTIONS
²Secure loose and protruding parts.
²Always use a safety chain system that is indepen-
dent of the lifting and towing equipment.
²Do not allow towing equipment to contact the dis-
abled vehicle's fuel tank.
²Do not allow anyone under the disabled vehicle
while it is lifted by the towing device.
Fig. 2 Vehicle Lifting LocationsÐTypical
0 - 10 LUBRICATION AND MAINTENANCEJ

ENGINE MAINTENANCE
INDEX
page page
Accessory Drive Belt....................... 21
Air Cleaner Element....................... 18
Air-Conditioner Compressor.................. 21
Battery................................. 20
Crankcase Ventilation System................ 19
Emission Control System................... 20
Engine Break-In.......................... 15
Engine Cooling System..................... 18
Engine Oil.............................. 15Engine Oil Change and Filter Replacement...... 16
Engine Oil Filter.......................... 17
Engine Supports.......................... 21
Exhaust System.......................... 21
Fuel Filter............................... 19
Fuel Usage StatementÐGas Engines.......... 19
Ignition Cables, Distributor Cap and Rotor....... 20
Rubber and Plastic Component Inspection....... 20
Spark Plugs............................. 20
ENGINE BREAK-IN
CAUTION: Wide open throttle operation in low
gears, before engine break-in period is complete,
can damage engine.
After first starting a new engine, allow it to idle for
15 seconds before shifting into a drive gear. Also:
²Drive the vehicle at varying speeds less than 88
km/h (55 mph) for the first 480 km (300 miles).
²Avoid fast acceleration and sudden stops.
²Do not drive at full-throttle for extended periods of
time.
²Do not drive at constant speeds.
²Do not idle the engine excessively.
A special break-in engine oil is not required. The
original engine oil installed is a high quality, energy
conserving lubricant. Special break-in oils are not
recommended. These oils could interfere with the
normal piston ring seating process.
New engines tend to consume more fuel and oil un-
til after the break-in period has ended.
ENGINE OIL
WARNING: NEW OR USED ENGINE OIL CAN BE IR-
RITATING TO THE SKIN. AVOID PROLONGED OR
REPEATED SKIN CONTACT WITH ENGINE OIL.
CONTAMINANTS IN USED ENGINE OIL, CAUSED BY
INTERNAL COMBUSTION, CAN BE HAZARDOUS TO
YOUR HEALTH. THOROUGHLY WASH EXPOSED
SKIN WITH SOAP AND WATER.
DO NOT WASH SKIN WITH GASOLINE, DIESEL
FUEL, THINNER, OR SOLVENTS, HEALTH PROB-
LEMS CAN RESULT.
DO NOT POLLUTE, DISPOSE OF USED ENGINE
OIL PROPERLY. CONTACT YOUR DEALER OR GOV-
ERNMENT AGENCY FOR LOCATION OF COLLEC-
TION CENTER IN YOUR AREA.
ENGINE OIL SPECIFICATION
CAUTION: Do not use non-detergent or straight
mineral oil when adding or changing crankcase lu-
bricant. Engine failure can result.
API SERVICE GRADE CERTIFIED
Use an engine oil that is API Service Grade Certi-
fied or an oil that conforms to the API Service Grade
SH or SH/CD. MOPAR provides engine oils that con-
form to all of these service grades.
SAE VISCOSITY
An SAE viscosity grade is used to specify the vis-
cosity grade of engine oil. SAE 30 specifies a single
viscosity engine oil. Engine oils also have multiple
viscosities. These are specified with a dual SAE vis-
cosity grade which indicates the cold-to-hot tempera-
ture viscosity range. Select an engine oil that is best
suited to your particular temperature range and vari-
ation (Fig.1).
ENERGY CONSERVING OIL
An Energy Conserving type oil is recommeded for
gasoline engines. They are designated as either EN-
ERGY CONSERVING or ENERGY CONSERVING
II.
Fig. 1 Temperature/Engine Oil Viscosity
JLUBRICATION AND MAINTENANCE 0 - 15

(2) Remove the air cleaner element from the body/
housing.
(3) Hold a shop light on throttle body side of ele-
ment. Inspect air intake side of element. If element
is saturated with oil or light is not visible, replace fil-
ter. If element is saturated with oil, perform crank-
case ventilation system tests.
(4) Wash the air cleaner cover and body/housing
(Fig. 10) with cleaning solvent and wipe dry.
(5) Install the air cleaner element and attach the
cover to the body/housing.
CRANKCASE VENTILATION SYSTEM
All Jeep 2.5L and 4.0L engines are equipped with a
crankcase ventilation (CCV) system. Refer to Group
25 Emissions, for additional information.
FUEL FILTER
The fuel filter requires service only when a fuel
contamination problem is suspected. For proper diag-
nostic and service procedures refer to Group 14, Fuel
System.
FUEL USAGE STATEMENTÐGAS ENGINES
Jeep vehicles are designed to meet all emission reg-
ulations and provide excellent fuel economy using
high quality unleaded gasoline. Only use unleaded
gasolines having a minimum posted octane of 87.
If a Jeep vehicle develops occasional light spark
knock (ping) at low engine speeds, this is not harm-
ful. However,continued heavy knock at high
speeds can cause damage and should be
checked immediately.
In addition to using unleaded gasoline with the
proper octane rating,those that contain deter-
gents, corrosion and stability additives are rec-
ommended.Using gasolines that have these
additives will help improve fuel economy, reduce
emissions and maintain vehicle performance.
Poor quality gasolinecan cause problems such
as hard starting, stalling and stumble. If these prob-
lems occur, use another brand of gasoline before con-
sidering servicing the vehicle.
GASOLINE/OXYGENATE BLENDS
Some fuel suppliers blend unleaded gasoline with
materials that contain oxygen such as alcohol, MTBE
and ETBE. The type and amount of oxygenate used
in the blend is important. The following are generally
used in gasoline blends:
ETHANOL
Ethanol (Ethyl or Grain Alcohol) properly blended,
is used as a mixture of 10 percent ethanol and 90
percent gasoline.Gasoline with ethanol may be
used in your vehicle.
METHANOL
CAUTION: Do not use gasolines containing metha-
nol. Use of methanol/gasoline blends may result in
starting and driveability problems. In addition, dam-
age may be done to critical fuel system compo-
nents.
Methanol (Methyl or Wood Alcohol) is used in a va-
riety of concentrations blended with unleaded gaso-
Fig. 9 Air Cleaner & Filter ElementÐ2.5L and 4.0L
Engines
Fig. 10 Air Cleaner Body/Housing & Cover
JLUBRICATION AND MAINTENANCE 0 - 19

pedal. The proper course of action is to bleed the sys-
tem, or replace thin drums and suspect quality brake
lines and hoses.
HARD PEDAL OR HIGH PEDAL EFFORT
A hard pedal or high pedal effort may be due to lin-
ing that is water soaked, contaminated, glazed, or
badly worn. The power booster or check valve could
also be faulty. Test the booster and valve as described
in this section.
BRAKE DRAG
Brake drag occurs when the lining is in constant
contact with the rotor or drum. Drag can occur at one
wheel, all wheels, fronts only, or rears only. It is a
product of incomplete brakeshoe release. Drag can be
minor or severe enough to overheat the linings, ro-
tors and drums. A drag condition also worsens as
temperature of the brake parts increases.
Brake drag also has a direct effect on fuel economy.
If undetected, minor brake drag can be misdiagnosed
as an engine or transmission/torque converter prob-
lem.
Minor drag will usually cause slight surface char-
ring of the lining. It can also generate hard spots in
rotors and drums from the overheat/cool down pro-
cess. In most cases, the rotors, drums, wheels and
tires are quite warm to the touch after the vehicle is
stopped.
Severe drag can char the brake lining all the way
through. It can also distort and score rotors and
drums to the point of replacement. The wheels, tires
and brake components will be extremely hot. In se-
vere cases, the lining may generate smoke as it chars
from overheating.
An additional cause of drag involves the use of in-
correct length caliper mounting bolts. Bolts that are
too long can cause a partial apply condition. The cor-
rect caliper bolts have a shank length of 67 mm
(2.637 in.), plus or minus 0.6 mm (0.0236 in.). Refer
to the Disc Brake service section for more detail on
caliper bolt dimensions and identification.
Some common causes of brake drag are:
²loose or damaged wheel bearing
²seized or sticking caliper or wheel cylinder piston
²caliper binding on bolts or slide surfaces
²wrong length caliper mounting bolts (too long)
²loose caliper mounting bracket
²distorted rotor, brake drum, or shoes
²brakeshoes binding on worn/damaged support
plates
²severely rusted/corroded components
²misassembled components.
If brake drag occurs at all wheels, the problem may
be related to a blocked master cylinder compensatorport or faulty power booster (binds-does not release).
The condition will worsen as brake temperature in-
creases.
The brakelight switch can also be a cause of drag.
An improperly mounted or adjusted brakelight
switch can prevent full brake pedal return. The re-
sult will be the same as if the master cylinder com-
pensator ports are blocked. The brakes would be
partially applied causing drag.
BRAKE FADE
Brake fade is a product of overheating caused by
brake drag. However, overheating and subsequent
fade can also be caused by riding the brake pedal,
making repeated high deceleration stops in a short
time span, or constant braking on steep roads. Refer
to the Brake Drag information in this section for
causes.
PEDAL PULSATION (NON-ABS BRAKES ONLY)
Pedal pulsation is caused by parts that are loose,
or beyond tolerance limits. This type of pulsation is
constant and will occur every time the brakes are ap-
plied.
Disc brake rotors with excessive lateral runout or
thickness variation, or out of round brake drums are
the primary causes of pulsation.
On vehicles with ABS brakes, remember that pedal
pulsation is normal during antilock mode brake
stops. If pulsation occurs during light to moderate
brake stops, a standard brake part is either loose, or
worn beyond tolerance.
BRAKE PULL
A front pull condition could be the result of:
²contaminated lining in one caliper
²seized caliper piston
²binding caliper
²wrong caliper mounting bolts (too long)
²loose caliper
²loose or corroded mounting bolts
²improper brakeshoes
²damaged rotor
²incorrect wheel bearing adjustment (at one wheel)
A worn, damaged wheel bearing or suspension com-
ponent are further causes of pull. A damaged front
tire (bruised, ply separation) can also cause pull.
Wrong caliper bolts (too long) will cause a partial ap-
ply condition and pull if only one caliper is involved.
A common and frequently misdiagnosed pull condi-
tion is where direction of pull changes after a few
stops. The cause is a combination of brake drag fol-
lowed by fade at the dragging brake unit.
As the dragging brake overheats, efficiency is so re-
duced that fade occurs. If the opposite brake unit is
still functioning normally, its braking effect is magni-
5 - 6 SERVICE BRAKE DIAGNOSISJ

temperature, coolant is allowed to flow to the radia-
tor. This provides quick engine warmup and overall
temperature control.
An arrow plus the wordUPis stamped on the
front flange next to the air bleed. The wordsTO
RADare stamped on one arm of the thermostat.
They indicate the proper installed position.
The same thermostat is used for winter and sum-
mer seasons. An engine should not be operated with-
out a thermostat, except for servicing or testing.
Operating without a thermostat causes other prob-
lems. These are: longer engine warmup time, unreli-
able warmup performance, increased exhaust
emissions and crankcase condensation. This conden-
sation can result in sludge formation.
CAUTION: Do not operate an engine without a ther-
mostat, except for servicing or testing.
ON-BOARD DIAGNOSTICS
XJ and YJ models are equipped with On-Board Di-
agnostics for certain cooling system components. Re-
fer to On-Board Diagnostics (OBD) in the Diagnosis
section of this group for additional information. If the
powertrain control module (PCM) detects low engine
coolant temperature, it will record a Diagnostic Trou-
ble Code (DTC) in the PCM memory. The DTC num-
ber for low coolant temperature is 17. Do not change
a thermostat for lack of heat as indicated by the in-
strument panel gauge or heater performance unless a
DTC number 17 is present. Refer to the Diagnosis
section of this group for other probable causes. For
other DTC numbers, refer to On-Board Diagnostics
in the General Diagnosis section of Group 14, Fuel
Systems.
The DTC can also be accessed through the DRB
scan tool. Refer to the appropriate Powertrain Diag-
nostic Procedures manual for diagnostic information
and operation of the DRB scan tool.
REMOVAL
WARNING: DO NOT LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND PRES-
SURIZED. SERIOUS BURNS FROM THE COOLANT
CAN OCCUR.
DO NOT WASTE reusable coolant. If the solution
is clean, drain the coolant into a clean container for
reuse.
(1) Drain the coolant from the radiator until the
level is below the thermostat housing.
WARNING: CONSTANT TENSION HOSE CLAMPS
ARE USED ON MOST COOLING SYSTEM HOSES.
WHEN REMOVING OR INSTALLING, USE ONLY
TOOLS DESIGNED FOR SERVICING THIS TYPE OF
CLAMP, SUCH AS SPECIAL CLAMP TOOL (NUMBER
6094) (FIG. 15). SNAP-ON CLAMP TOOL (NUMBER
HPC-20) MAY BE USED FOR LARGER CLAMPS. AL-
WAYS WEAR SAFETY GLASSES WHEN SERVICING
CONSTANT TENSION CLAMPS.
CAUTION: A number or letter is stamped into the
tongue of constant tension clamps (Fig. 16). If re-
placement is necessary, use only an original equip-
ment clamp with matching number or letter.
(2) Remove radiator upper hose and heater hose at
thermostat housing.
(3) Disconnect wiring connector at engine coolant
temperature sensor.
(4) Remove thermostat housing mounting bolts,
thermostat housing, gasket and thermostat (Fig. 17).
Discard old gasket.
(5) Clean the gasket mating surfaces.
Fig. 13 XJ Models with 4.0L 6-Cylinder EngineÐ
Without A/C
Fig. 14 XJ Models With 4.0L 6-Cylinder EngineÐ
With A/C
7 - 18 COOLING SYSTEM SERVICE PROCEDURESJ

subjected to a high torque load, deposits partially liq-
uefy and bridge the gap between electrodes (Fig. 21).
This short circuits the electrodes. Spark plugs with
electrode gap bridging can be cleaned using standard
procedures.
SCAVENGER DEPOSITS
Fuel scavenger deposits may be either white or yel-
low (Fig. 22). They may appear to be harmful, but
this is a normal condition caused by chemical addi-
tives in certain fuels. These additives are designed to
change the chemical nature of deposits and decrease
spark plug misfire tendencies. Notice that accumula-
tion on the ground electrode and shell area may be
heavy, but the deposits are easily removed. Sparkplugs with scavenger deposits can be considered nor-
mal in condition and can be cleaned using standard
procedures.
CHIPPED ELECTRODE INSULATOR
A chipped electrode insulator usually results from
bending the center electrode while adjusting the
spark plug electrode gap. Under certain conditions,
severe detonation can also separate the insulator
from the center electrode (Fig. 23). Spark plugs with
this condition must be replaced.
PREIGNITION DAMAGE
Preignition damage is usually caused by excessive
combustion chamber temperature. The center elec-
trode dissolves first and the ground electrode dis-
solves somewhat latter (Fig. 24). Insulators appear
relatively deposit free. Determine if the spark plug
has the correct heat range rating for the engine. De-
termine if ignition timing is over advanced, or if
other operating conditions are causing engine over-
heating. (The heat range rating refers to the operat-
ing temperature of a particular type spark plug.
Spark plugs are designed to operate within specific
Fig. 20 Oil or Ash Encrusted
Fig. 21 Electrode Gap Bridging
Fig. 22 Scavenger Deposits
Fig. 23 Chipped Electrode Insulator
JIGNITION SYSTEMS 8D - 13

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

INSTRUMENT PANEL AND GAUGESÐYJ
CONTENTS
page page
INSTRUMENT PANEL AND GAUGESÐYJ..... 22
DIAGNOSIS............................ 23
GENERAL INFORMATION................. 20SERVICE PROCEDURES.................. 31
SPECIFICATIONS........................ 39
GENERAL INFORMATION
Following are general descriptions of major instru-
ment panel components. Refer to Group 8W - Wiring
Diagrams for complete circuit descriptions and dia-
grams.
INSTRUMENT PANEL
Modular instrument panel construction allows all
gauges and controls to be serviced from the front of
the panel. In addition, most instrument panel wiring
and heater components can be accessed without com-
plete instrument panel removal.
Removal of the left instrument cluster bezel allows
access to the main cluster assembly and most
switches. Removal of the center cluster bezel allows
access to the gauge package cluster assembly, the
heater controls, and the radio. Removal of the cluster
assemblies allows access to the individual gauges, il-
lumination and indicator lamp bulbs, printed cir-
cuits, and most wiring.
INSTRUMENT CLUSTERS
The instrument cluster used on YJ (Wrangler) mod-
els consists of two separate assemblies. The main
cluster assembly is located on the left side of the in-
strument panel, centered over the steering column
opening. The gauge package cluster assembly is lo-
cated near the center of the instrument panel. Each
cluster assembly is served by a separate printed cir-
cuit and wiring connector. Some variations of each
cluster exist due to optional equipment and regula-
tory requirements.
The main cluster assembly includes a speedometer/
odometer/trip odometer and a tachometer. It also in-
cludes provisions for the following indicator lamps:
²anti-lock brake system lamp
²brake warning lamp
²headlamp high beam indicator lamp
²malfunction indicator (Check Engine) lamp
²seat belt reminder lamp²turn signal indicator lamps
²upshift indicator lamp.
The gauge package cluster assembly includes a
four-wheel drive indicator lamp and the following
gauges:
²coolant temperature gauge
²fuel gauge
²oil pressure gauge
²voltmeter.
GAUGES
With the ignition switch in the ON or START posi-
tion, voltage is supplied to all gauges through the
two cluster printed circuits. 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. How-
ever, the gauges do not accurately indicate any vehi-
cle 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).
8E - 24 INSTRUMENT PANEL AND GAUGESÐYJJ