ignition JEEP CHEROKEE 1994 Service Repair Manual

60,000 MILES (96 500 KM) OR AT 48 MONTHS.
²Replace air cleaner filter.
²Replace distributor cap and rotor.
²Replace ignition wires.
²Replace spark plugs.
²Adjust or replace drive belt.
²Check engine coolant level, hoses and clamps.
²Change engine oil.
²Replace engine oil filter.
²Check exhaust system.
²Replace fuel filter (not required for Calif. vehicles).
²Lubricate steering linkage (4x4 models).
²Lubricate propeller shaft universal joints.
²Check fluid level in battery.
²Drain and refill automatic transmission.
²Drain and refill transfer case.
²Rotate Tires.
67,500 MILES (108 500 KM) OR AT 54
MONTHS
²Check engine coolant level, hoses and clamps.
²Change engine oil.
²Replace engine oil filter.
²Check exhaust system.
²Lubricate steering linkage (4x4 models).
²Lubricate propeller shaft universal joints.
²Rotate Tires.
75,000 MILES (120 500 KM) OR AT 60
MONTHS
²Check engine coolant level, hoses and clamps.
²Change engine oil.
²Replace engine oil filter.
²Check exhaust system.
²Lubricate steering linkage (4x4 models).
²Lubricate propeller shaft universal joints.
²Drain and refill manual transmission.
²Rotate Tires.
82,500 MILES (133 000 KM) OR AT 66
MONTHS
²Flush and replace engine coolant.
²Check engine coolant system, hoses and clamps.
²Change engine oil.
²Replace engine oil filter.
²Check exhaust system.
²Lubricate steering linkage (4x4 models).
²Lubricate propeller shaft universal joints.
²Rotate Tires.
90,000 MILES (145 000 KM) OR AT 72
MONTHS
²Replace air cleaner filter.
²Replace spark plugs.
²Adjust drive belt.
²Check engine coolant level, hoses and clamps.
²Change engine oil.
²Replace engine oil filter.²Check exhaust system.
²Lubricate steering linkage (4x4 models).
²Lubricate propeller shaft universal joints.
²Check fluid level in battery.
²Drain and refill automatic transmission.
²Drain and refill transfer case.
²Rotate Tires.
97,500 MILES (157 000 KM) OR AT 78
MONTHS
²Check engine coolant level, hoses and clamps.
²Change engine oil.
²Replace engine oil filter.
²Check exhaust system.
²Lubricate steering linkage (4x4 models).
²Lubricate propeller shaft universal joints.
²Rotate Tires.
105,000 MILES (169 000 KM) OR AT 84
MONTHS
²Check engine coolant level, hoses and clamps.
²Change engine oil.
²Replace engine oil filter.
²Check exhaust system.
²Lubricate steering linkage (4x4 models).
²Lubricate propeller shaft universal joints.
²Rotate Tires.
112,500 MILES (181 000 KM) OR AT 90
MONTHS
²Flush and replace engine coolant.
²Check engine coolant system hoses and clamps.
²Change engine oil.
²Replace engine oil filter.
²Check exhaust system.
²Lubricate steering linkage (4x4 models).
²Lubricate propeller shaft universal joints.
²Rotate Tires.
120,000 MILES (193 000 KM) OR AT 96
MONTHS
²Replace air cleaner filter.
²Replace distributor cap and rotor.
²Replace ignition wires.
²Replace spark plugs.
²Adjust or replace drive belt.
²Check engine coolant level, hoses and clamps.
²Change engine oil.
²Replace engine oil filter.
²Check exhaust system.
²Replace fuel filter (not required for Calif. vehicles).
²Lubricate steering linkage (4x4 models).
²Lubricate propeller shaft universal joints.
²Check fluid level in battery.
²Drain and refill automatic transmission.
²Drain and refill transfer case.
²Rotate Tires.
0 - 6 LUBRICATION AND MAINTENANCEJ

²if the vehicle is damaged, secure the loose and pro-
truding parts;
²always use a safety chain system that is indepen-
dent of the lifting and towing equipment;
²do not allow any of the towing equipment to con-
tact the disabled vehicle's fuel tank;
²do not allow anyone to be under the disabled vehi-
cle while it is lifted by the towing equipment;
²do not allow passengers to ride in a vehicle being
towed;
²always observe all state and local laws involving
warning signals, night illumination, speed, etc.
²do not attempt a towing operation that could jeop-
ardize the safety of the operator, bystanders or other
motorists;
²do not exceed a towing speed of 48 km/h (30 mph);
²avoid towing distances of more than 24 km (15
miles) whenever possible; and
²do not attach tow chains or a tow sling to a
bumper, the steering linkage, the universal joints,
the constant velocity (CV) joints, or a drive shaft.
CLEARANCES AND RAMP ANGLE
SURFACE CLEARANCE
The end of the disabled vehicle that is attached to
the tow vehicle should be lifted a minimum of 10 cm
or four inches off the surface. Inspect to ensure that
the opposite end of the disabled vehicle has clearance
from the surface.
RAMP ANGLEÐFLAT-BED TOWING
If a vehicle with flat-bed towing equipment is used,
the approach ramp angle should not exceed 15 de-
grees.
SLING-TYPE, FRONT-END TOWING
XJ VEHICLES
Use the following guidelines when the tow vehicle
is attached to the front end of a disabled vehicle.
(1) Always tow with the front wheels lifted off the
surface and turned all the way to the right.
(2) Attach a J-hook to the disabled vehicle at the
left side of the axle (Fig. 10).
(3) Position the sling crossbar close to the J-hook
and below the front bumper (Fig. 11).
(4) Secure a chain to the right side of vehicle by
placing it over the axle shaft tube and attaching it to
a structural member.
(5) Attach the safety chains to the vehicle.
2WD With Manual Or Automatic Transmission
(6) Turn the ignition switch to the OFF position to
unlock the steering wheel.
(7) Shift the transmission to NEUTRAL, mark the
drive shaft and axle drive pinion gear shaft yoke for
installation reference. Remove the drive shaft from
the vehicle.(8) Cover the exposed end of the transmission ex-
tension housing and the universal joints. Store the
drive shaft in a safe place.
4WD, Command-Trac (231 Part-Time 4WD
Transfer Case) And Manual Transmission
(6) Turn the ignition switch to the OFF position to
unlock the steering wheel.
When the transfer case is in the NEUTRAL po-
sition, both axles are disengaged from the pow-
ertrain. This allows the vehicle to be towed
without removing the drive shafts.
(7) Shift the manual transmission into a forward
gear and the transfer case to NEUTRAL.
4WD, Command-Trac (231 Part-Time 4WD
Transfer Case) And Automatic Transmission
(6) Turn the ignition switch to the OFF position to
unlock the steering wheel.
Fig. 10 Sling-Type, Front-End Towing (XJ Front
View)
Fig. 11 Sling-Type, Front-End Towing (XJ Rear
View)
JLUBRICATION AND MAINTENANCE 0 - 9

When the transfer case is in the NEUTRAL po-
sition, both axles are disengaged from the pow-
ertrain. This allows the vehicle to be towed
without removing the drive shafts.
(7) Shift the automatic transmission to PARK and
the transfer case to NEUTRAL.
4WD, Selec-Trac (242 Full-Time 4WD Transfer
Case) And Automatic Transmission
(6) Turn the ignition switch to the OFF position to
unlock the steering wheel.
When the transfer case is in the NEUTRAL po-
sition, both axles are disengaged from the pow-
ertrain. This allows the vehicle to be towed
without removing the drive shafts.
(7) Shift the automatic transmission to PARK and
the transfer case to NEUTRAL.
YJ VEHICLES
Use the following guidelines when the tow vehicle
is attached to the front of a disabled vehicle.
(1) Always tow with the front wheels lifted off the
surface and turned all the way to the right.
CAUTION: Use tow chains with T-hooks for con-
necting to the disabled vehicle's frame rails (Fig.
12). Never use J-hooks.
(2) Attach the T-hooks to the slots in the front end
of each frame rail (Fig. 13).
(3) Position each safety chain over the top of each
front spring and inboard of each front spring shackle.
(4) Double wrap each chain.
(5) Position the sling crossbar under the front
bumper.
Command-Trac (231 Part-Time 4WD Transfer
Case) And Manual Transmission
(6) Turn the ignition switch to the OFF position to
unlock the steering wheel.
When the transfer case is in the NEUTRAL po-
sition, both axles are disengaged from the pow-
ertrain. This allows the vehicle to be towed
without removing the drive shafts.
(7) Shift the manual transmission to a forward
gear and the transfer case to NEUTRAL.Command-Trac (231 Part-Time 4WD Transfer
Case) And Automatic Transmission
(6) Turn the ignition switch to the OFF position to
unlock the steering wheel.
When the transfer case is in the NEUTRAL po-
sition, both axles are disengaged from the pow-
ertrain. This allows the vehicle to be towed
without removing the drive shafts.
(7) Shift the automatic transmission to PARK and
the transfer case to NEUTRAL.
SLING-TYPE, REAR-END TOWING
YJ VEHICLESÐUse wheel-lift equipment ONLY
when towing from the rear end of the vehicle is nec-
essary.
XJ VEHICLESÐUse the following guidelines
when the tow vehicle is attached to the rear of the
disabled vehicle.
(1) Attach J-hooks around the axle shaft tubes out-
board of the shock absorber.
(2) Place the sling crossbar under and forward of
the bumper.
(3) Attach safety chains around the frame rails.
2WD With Manual Or Automatic Transmission
(1) Attach J-hooks around the axle shaft tubes out-
board of the shock absorber.
(2) Place the sling crossbar under and forward of
the bumper.
(3) Attach safety chains around the frame rails.
(4) Turn the ignition switch to the OFF position to
unlock the steering wheel.
(5) Clamp the steering wheel with the front wheels
in the straight ahead position. Do not use the steer-
ing column lock as a substitute for a clamping de-
vice.
(6) Shift the transmission to NEUTRAL.
Fig. 12 Tow Chains & Hooks
Fig. 13 Sling-Type, Front-End Towing (YJ Vehicles)
0 - 10 LUBRICATION AND MAINTENANCEJ

4WD, Command-Trac (231 Part-Time 4WD
Transfer Case) And Manual Transmission
(1) Attach J-hooks around the axle shaft tubes out-
board of the shock absorber.
(2) Place the sling crossbar under and forward of
the bumper.
(3) Attach safety chains around the frame rails.
(4) Turn the ignition switch to the OFF position to
unlock the steering column.
(5) Clamp the steering wheel with the front wheels
in the straight ahead position. Do not use the steer-
ing column lock as a substitute for a clamping de-
vice.
When the transfer case is in the NEUTRAL po-
sition, both axles are disengaged from the pow-
ertrain. This allows the vehicle to be towed
without removing the drive shafts.
(6) Shift the transmission to a forward gear and
the transfer case to NEUTRAL.
4WD, Command-Trac (231 Part-Time 4WD
Transfer Case) And Automatic Transmission
(1) Attach J-hooks around the axle shaft tubes out-
board of the shock absorber.
(2) Place the sling crossbar under and forward of
the bumper.
(3) Attach safety chains around the frame rails.
(4) Turn the ignition switch to the OFF position to
unlock the steering column.
(5) Clamp the steering wheel with the front wheels
in the straight ahead position. Do not use the steer-
ing column lock as a substitute for a clamping de-
vice.
When the transfer case is in the NEUTRAL po-
sition, both axles are disengaged from the pow-
ertrain. This allows the vehicle to be towed
without removing the drive shafts.
(6) Shift the transmission to PARK and the trans-
fer case to NEUTRAL.
4WD, Selec-Trac (242 Full-Time 4WD Transfer
Case) And Automatic Transmission
(1) Attach J-hooks around the axle shaft tubes out-
board of the shock absorber.
(2) Place the sling crossbar under and forward of
the bumper.
(3) Attach safety chains around the frame rails.
(4) Turn the ignition switch to the OFF position to
unlock the steering column.
(5) Clamp the steering wheel with the front wheels
in the straight ahead position. Do not use the steer-
ing column lock as a substitute for a clamping de-
vice.
When the transfer case is in the NEUTRAL po-
sition, both axles are disengaged from the pow-
ertrain. This allows the vehicle to be towed
without removing the drive shafts.
(6) Shift the transmission to PARK and the trans-
fer case to NEUTRAL.TOWING WHEN IGNITION KEYS ARE NOT
AVAILABLE
VEHICLE DOORS UNLOCKED
2WD Vehicles
Either one of two methods can be used:
²tow the vehicle with the drive shaft removed (refer
to Sling-Type, Front-End Towing); or
²place a tow dolly under the rear wheels (Fig. 14)
and tow with the front end raised (refer to Sling-
Type, Front-End Towing).
4WD, Command-Trac (231 Part-Time 4WD
Transfer Case) And Manual Transmission
(1) Shift the manual transmission to a forward
gear.
When the transfer case is in the NEUTRAL po-
sition, both axles are disengaged from the pow-
ertrain. This allows the vehicle to be towed
without removing the drive shafts.
(2) Shift the transfer case to NEUTRAL.
(3) The vehicle can now be towed with the front
wheels raised (refer to Sling-Type, Front-End Tow-
ing).
4WD, Command-Trac (231 Part-Time 4WD
Transfer Case) And Automatic Transmission
(1) Check and ensure that the automatic transmis-
sion is in PARK.
When the transfer case is in the NEUTRAL po-
sition, both axles are disengaged from the pow-
ertrain. This allows the vehicle to be towed
without removing the drive shafts.
(2) Shift the transfer case to NEUTRAL.
(3) The vehicle can now be towed with the front
wheels raised (refer to Sling-Type, Front-End Tow-
ing).
4WD, Selec-Trac (242 Full-Time 4WD Transfer
Case) And Automatic Transmission
(1) Check and ensure that the automatic transmis-
sion is in PARK.
Fig. 14 Sling-Type, Front-End Towing With Rear
Wheels On A Tow Dolly
JLUBRICATION AND MAINTENANCE 0 - 11

When the transfer case is in the NEUTRAL po-
sition, both axles are disengaged from the pow-
ertrain. This allows the vehicle to be towed
without removing the drive shafts.
(2) Shift the transfer case to NEUTRAL.
(3) The vehicle can now be towed with the front
wheels raised (refer to Sling-Type, Front-End Tow-
ing).
VEHICLE DOORS LOCKED
Place a tow dolly under the rear wheels (Fig. 14)
and tow with the front end raised (refer to Sling-
Type, Front-End Towing).
4WD EMERGENCY TOWINGÐTRANSFER CASE
NOT SHIFTED TO NEUTRAL
When a situation arises and the transfer case can-
not be shifted to NEUTRAL, any of the following
methods can be used to tow a 4WD vehicle.
Drive shafts not removed, place the rear
wheels on a tow dolly and tow with the front
end raised.
Drive shafts not removed, place the front
wheels on a tow dolly and tow with the rear end
raised.
Rear drive shaft removed, tow with the front
end raised.
Front drive shaft removed, tow with the rear
end raised.
Both drive shafts removed, tow with all four
wheels on the road surface.
(1) Turn ignition key switch to the unlocked (OFF)
position.
(2) Shift the transmission to the NEUTRAL posi-
tion.
(3) Determine the method by which the vehicle
will be towed and prepare the vehicle for towing.
(4) Connect the vehicle to the tow vehicle. Refer to
the applicable procedure.
FLAT TOWING (4 TIRES/WHEELS ON
SURFACE)
Tow a vehicle in this manner only when all four
wheels will freely rotate. Prepare the vehicle accord-
ing to the following procedures.
2WD VEHICLES
(1) Mark the drive shaft and the axle drive pinion
gear shaft yoke for installation alignment reference.
(2) Remove the drive shaft. Install a protective
covering over the drive shaft U-joints to retain them
assembled and protected.
(3) Cover the open end of the transmission exten-
sion housing.4WD VEHICLES
(1) Mark the drive shafts and the axle drive pinion
gear shaft yokes for installation alignment reference.
(2) Remove the drive shafts. Install a protective
covering over the drive shaft U-joints/CV-joints to re-
tain them assembled and protected.
(3) Cover the exposed ends of the transfer case.
CAUTION: Whenever a drive shaft has been re-
moved and installed, check the transmission fluid
level of the transmission and transfer case. Driving
a vehicle with low tranfer case fluid can damage the
transmission and transfer case.
EMERGENCY TOW HOOKS
WARNING: REMAIN AT A SAFE DISTANCE FROM A
VEHICLE THAT IS BEING TOWED VIA ITS TOW
HOOKS. THE TOW STRAPS/CHAINS COULD POSSI-
BLY BREAK AND CAUSE SERIOUS INJURY.
Some Jeeptvehicles are equipped with emergency
tow hooks located at the front end (Fig. 15). Some
Jeeptvehicles also have emergency tow hooks lo-
cated at the rear ende. The tow hooks should be used
forEMERGENCYpurposes only.
CAUTION: DO NOT use emergency tow hooks for
tow truck hook-up or highway towing.
Fig. 15 Emergency Front Tow HooksÐXJ & YJ
Vehicles
0 - 12 LUBRICATION AND MAINTENANCEJ

ENGINE MAINTENANCE
INDEX
page page
Accessory Drive Belt...................... 20
Air-Conditioner Compressor/Hoses/Fittings...... 21
Battery................................ 18
Cooling System.......................... 16
Crankcase Ventilation System............... 17
Engine Air Cleaner Filter Element............ 16
Engine Break-In......................... 13
Engine Oil.............................. 13Engine Oil Change and Filter Replacement..... 15
Engine Oil Filter......................... 14
Engine Supports......................... 20
Exhaust System......................... 20
Fuel Usage StatementÐGas Engines......... 17
Ignition Cables, Distributor Cap and Rotor...... 18
Rubber and Plastic Ducts/Hoses/Tubing....... 19
Spark Plugs............................ 18
ENGINE BREAK-IN
After first starting a new engine, allow it to idle
and warm up for at least 15 seconds before shifting
the transmission into a drive gear.
Drive the vehicle at:
²varying speeds less than 80 km/h (50 mph) for the
first 160 km (100 miles), and
²speeds less than 88 km/h (55 mph) for the first 800
km (500 miles).
Avoid driving at full-throttle for extended periods
of time. Also, avoid fast acceleration and sudden
stops.
A special break-in engine oil is not required. The
original oil installed in a vehicle is a quality lubri-
cant. There is no requirement to have the oil
changed or the oil filter replaced until the first
scheduled maintenance interval.
The engine oil, coolant and all the other engine re-
lated fluid levels should be determined on a regular
basis.
ENGINE OIL
SPECIFICATIONS
API SERVICE GRADE
For maximum engine protection during all driving
conditions, install an engine oil that conforms to API
Service Grade. MOPAR Engine Oil conforms to all of
these API Service Grades.
SAE VISCOSITY
SAE designated multi-viscosity grade engine oil is
to protect engines. This type of engine oil can usually
be installed and remain in the engine until the next
scheduled oil change. Select the engine oil viscosity
according to the lowest ambient air temperature ex-
pected before the next scheduled oil change (Fig.1).
Low viscosity engine oil allows easier engine starting
during cold weather. SAE 5W-30 viscosity engine oil
is recommended when the ambient air temperatures
consistently decrease to below 10ÉF (-12ÉC).ENERGY CONSERVING OIL
In selecting the correct API grade and SAE grade,
anENERGY CONSERVINGtype engine oil is also
recommended.
CONTAINER IDENTIFICATION
Standard engine oil notations have been adopted
for selection of engine oil. The notations are located
on side of plastic bottles and on the top of engine oil
cans (Fig. 2).
²The top, outer field contains theAPI Service
Gradenotation for the engine oil.
Fig. 1 Temperature/Engine Oil Viscosity
Fig. 2 Engine Oil Container Standard Notations
JLUBRICATION AND MAINTENANCE 0 - 13

In areas of the country where carbon monoxide lev-
els are high, gasolines are being treated with oxy-
genated materials such as MTBE, ETBE and
ethanol.
Chrysler Corporation supports these efforts toward
cleaner air and recommends the use of these gaso-
lines as they become available.
IGNITION CABLES, DISTRIBUTOR CAP AND
ROTOR
REQUIRED IGNITION SYSTEM MAINTENANCE
The ignition cables, distributor cap and rotor must
be replaced after each 96 000-km (60,000-miles). Re-
fer to Group 8DÐIgnition Systems for additional in-
formation.
IGNITION TIMING
The ignition timing for 2.5L and 4.0L engines is
not adjustable. Refer to the specifications listed on
the engine Emission Control Information Label. Re-
fer to Group 25ÐEmission Control Systems for addi-
tional information.
SPARK PLUGS
REQUIRED MAINTENANCE
The spark plugs must be replaced after each 48
000-km (30,000-miles). Refer to the Spark Plugs
chart below and to Group 8DÐIgnition Systems for
additional information.
BATTERY
RECOMMENDED MAINTENANCE
The battery electrolyte level should be checked and
the cable clamps should be inspected for corrosion.
This should be done when the oil is changed and the
oil filter is replaced.
The battery cables should be inspected for abnor-
mal clamp and battery terminal post corrosion. Ser-
vice the terminals and cable clamps as necessary.In addition, the general condition of the battery
should be determined before the start of cold and hot
weather seasons. If the battery condition is marginal
or worse, it should be replaced.
Care should be taken when disposing a bat-
tery after removal from a vehicle. Lead-acid bat-
teries are highly poisonous and, when
indiscriminately disposed, could create a prob-
lem for the environment. Contact the applicable
local city or county government agency to deter-
mine where automobile (lead-acid) batteries can
be properly disposed in the local area.
INSPECTION/SERVICE
WARNING: WEAR SAFETY GLASSES, RUBBER
GLOVES AND PROTECTIVE CLOTHING WHEN HAN-
DLING/SERVICING A BATTERY. THE BATTERY
ELECTROLYTE CONTAINS SULFURIC ACID AND
WILL CAUSE HARM IF IT CONTACTS SKIN, EYES
OR CLOTHING. IT WILL ALSO DAMAGE PAINTED
(AS WELL AS UN-PAINTED) SURFACES OF A VEHI-
CLE. IF SULFURIC ACID CONTACTS ANY OF
THESE, FLUSH IMMEDIATELY WITH LARGE
AMOUNTS OF WATER. IF SULFURIC ACID CON-
TACTS SKIN OR EYES, GET IMMEDIATE MEDICAL
ATTENTION. DO NOT SMOKE IN THE VICINITY OF
A BATTERY. KEEP OPEN FLAMES AND SPARKS
AWAY FROM BATTERY FILLER CAPS BECAUSE
EXPLOSIVE GAS IS ALWAYS PRESENT.
(1) Disconnect the battery negative cable and then
the positive cable.
(2) Clean the battery cable clamps and terminal
posts with a wire brush and a battery terminal
cleaner.
(3) Pry the battery cell filler caps upward to re-
move them and inspect each filler well (low-mainte-
nance batteries only, not applicable to maintenance-
free batteries). It could possibly be necessary to
loosen the battery holddown clamp to remove the
caps. Maintain the electrolyte level above the battery
plates and at the bottom of the filler well ring. Add
distilled water or low-mineral content drinking wa-
ter, if necessary. In freezing weather (below 0ÉC/
32ÉF), add the water just before driving to ensure
that it mixes thoroughly with the electrolyte. This
will prevent it from freezing.
(4) Remove the battery holddown strap and clean
the battery case/battery tray.Clean with bicarbonate
of soda (baking soda) and water. Rinse and dry the
battery case/tray thoroughly after cleaning.
(5) Position the battery in the tray and install the
holddown strap.Do not over-tighten the nuts.
(6) Connect the battery positive cable and then the
negative cable to the battery.
SPARK PLUGS
0 - 18 LUBRICATION AND MAINTENANCEJ

(5) Inspect the reservoir rubber diaphragm seal for
cracks, cuts and distortion.
(6) Inspect the brake fluid tubing fittings and the
master cylinder housing for indications of fluid leak-
age. Repair as necessary.
(7) Install the brake fluid reservoir cover.
ANTI-LOCK BRAKE SYSTEMÐXJ VEHICLES
The anti-lock brake system fluid reservoir for XJ
Vehicles is located in the engine compartment at the
left side of the dash panel.
(1) Turn the ignition switch ON and allow the
pump motor to operate until it automatically de-en-
ergizes.
(2) Clean the cover before removing it.
CAUTION: Over-filling could cause fluid overflow
and possible reservoir damage when the pump mo-
tor energizes.
(3) The brake fluid level should be no lower than
the MIN arrow indicator on the side of the reservoir
(Fig. 8). If not, add brake fluid as necessary. Raise
the fluid level to the MAX arrow indicator only. Do
not over-fill the reservoir.
(4) Turn the ignition switch OFF.
BRAKE SYSTEM INSPECTION
BRAKE FLUID HOSES/TUBING
(1) Inspect all brake fluid rubber hoses (Fig. 9) for
cracks, swelling, kinks, a distorted condition and
fluid leakage.
(2) Inspect the brake fluid hoses and tubing that
are routed along the frame rail.
PADS/LININGS, ADJUSTER, WHEEL CYLINDERS AND
CALIPER
The front disk brake pads can be visually inspected
via the brake caliper inspection ports.(1) Inspect the brake pads and linings for excessive
wear, cracks, charred surfaces and broken rivets.
(2) Inspect the brake pads and linings for contam-
ination with brake fluid, axle lubricant and/or an-
other fluid.
(3) Replace the brake pads and/or linings if they
are worn to within 0.78 mm (1/32 in) of the rivet
head.
(4) Operate the rear brake self-adjuster lever and
pivot. Test the operation of the self-adjuster screw for
ease of movement.
(5) Inspect the self-adjuster components for bent
areas, frayed cables, loose or overheated springs, and
a binding condition.
Fig. 7 Reservoir Fluid LevelÐTypicalFig. 8 Reservoir Fluid LevelÐAnti-Lock Brake
System
Fig. 9 Rubber Brake Fluid HoseÐTypical
JLUBRICATION AND MAINTENANCE 0 - 33

MULTI-PORT FUEL INJECTION (MFI)ÐCOMPONENT DESCRIPTION/SYSTEM
OPERATION
INDEX
page page
Air Conditioning (A/C) Clutch RelayÐPCM Output.24
Air Conditioning (A/C) ControlsÐPCM Input.... 19
Auto Shut Down (ASD) RelayÐPCM Output.... 24
Automatic Shut Down (ASD) SenseÐPCM Input . 19
Battery VoltageÐPCM Input................ 19
Brake SwitchÐPCM Input.................. 20
Camshaft Position SensorÐPCM Input........ 20
Crankshaft Position SensorÐPCM Input....... 20
Data Link ConnectorÐPCM Input............ 20
Data Link ConnectorÐPCM Output........... 24
EMR LampÐPCM Output.................. 24
Engine Coolant Temperature SensorÐPCM Input . 21
Extended Idle SwitchÐPCM Input............ 21
Fuel InjectorsÐPCM Output................ 25
Fuel Pressure Regulator................... 30
Fuel Pump RelayÐPCM Output............. 25
Fuel Rail............................... 30
General Information....................... 17
Generator FieldÐPCM Output............... 25
Generator LampÐPCM Output.............. 25
Idle Air Control (IAC) MotorÐPCM Output...... 25
Ignition Circuit SenseÐPCM Input............ 21
Ignition CoilÐPCM Output.................. 26Intake Air Temperature SensorÐPCM Input.... 20
Malfunction Indicator LampÐPCM Output...... 26
Manifold Absolute Pressure (MAP) SensorÐ
PCM Input............................ 21
Open Loop/Closed Loop Modes of Operation . . . 27
Overdrive/Override Switch.................. 22
Oxygen (O2S) SensorÐPCM Input........... 22
Park/Neutral SwitchÐPCM Input............. 22
Power Ground........................... 22
Power Steering Pressure SwitchÐPCM Input . . . 22
Powertrain Control Module (PCM)............ 18
Radiator Fan RelayÐPCM Output............ 26
SCI ReceiveÐPCM Input.................. 22
SCI TransmitÐPCM Output................. 26
Sensor ReturnÐPCM Input................. 23
Shift IndicatorÐPCM Output................ 26
Speed ControlÐPCM Input................. 23
Speed ControlÐPCM Output................ 27
TachometerÐPCM Output.................. 27
Throttle Body............................ 29
Throttle Position Sensor (TPS)ÐPCM Input..... 23
Torque Converter Clutch RelayÐPCM Output . . . 27
Vehicle Speed SensorÐPCM Input........... 23
GENERAL INFORMATION
All 2.5L 4 cylinder and 4.0L 6 cylinder engines are
equipped with sequential Multi-Port Fuel Injection
(MFI). The MFI system provides precise air/fuel ra-
tios for all driving conditions.
The Powertrain Control Module (PCM) operates
the fuel system. The PCM was formerly referred to
as the SBEC or engine controller. The PCM is a pre-
programmed, dual microprocessor digital computer.
It regulates ignition timing, air-fuel ratio, emission
control devices, charging system, speed control, air
conditioning compressor clutch engagement and idle
speed. The PCM can adapt its programming to meet
changing operating conditions.
Powertrain Control Module (PCM) Inputsrep-
resent the instantaneous engine operating conditions.
Air-fuel mixture and ignition timing calibrations for
various driving and atmospheric conditions are pre-
programmed into the PCM. The PCM monitors and
analyzes various inputs. It then computes engine fuel
and ignition timing requirements based on these in-
puts. Fuel delivery control and ignition timing will
then be adjusted accordingly.
Other inputs to the PCM are provided by the brake
light switch, air conditioning select switch and the
speed control switches. All inputs to the PCM are
converted into signals.
Electrically operated fuel injectors spray fuel in
precise metered amounts into the intake port directlyabove the intake valve. The injectors are fired in a
specific sequence by the PCM. The PCM maintains
an air/fuel ratio of 14.7 to 1 by constantly adjusting
injector pulse width. Injector pulse width is the
length of time that the injector opens and sprays fuel
into the chamber. The PCM adjusts injector pulse
width by opening and closing the ground path to the
injector.
Manifold absolute pressure (air density) and engine
rpm (speed) are the primary inputs that determine
fuel injector pulse width. The PCM also monitors
other inputs when adjusting air-fuel ratio.
Inputs That Effect Fuel Injector Pulse Width
²Exhaust gas oxygen content
²Engine coolant temperature
²Manifold absolute pressure (MAP)
²Engine speed
²Throttle position
²Battery voltage
²Air conditioning selection
²Transmission gear selection (automatic transmis-
sions only)
²Speed control
The powertrain control module (PCM) adjusts igni-
tion timing by controlling ignition coil operation. The
ignition coil receives battery voltage when the igni-
tion key is in the run or starter position. The PCM
provides a ground for the ignition coil. The coil dis-
JFUEL SYSTEM 14 - 17

charges when the PCM supplies a ground. By switch-
ing the ground path on and off, the PCM regulates
ignition timing.
The sensors and switches that provide inputs to the
powertrain control module (PCM) comprise the En-
gine Control System. It is also comprised of the PCM
Outputs (engine control devices that the are operated
by the PCM).
SYSTEM DIAGNOSIS
The powertrain control module (PCM) tests many
of its own input and output circuits. If a Diagnostic
Trouble Code (DTC) is found in a major system, this
information is stored in the PCM memory. Refer to
On-Board Diagnostics in the MFI SystemÐGeneral
Diagnosis section of this group for DTC information.
POWERTRAIN CONTROL MODULE (PCM)
The PCM operates the fuel system. The PCM was
formerly referred to as the SBEC or engine control-
ler. The PCM is a pre-programmed, dual micropro-
cessor digital computer. It regulates ignition timing,
air-fuel ratio, emission control devices, charging sys-
tem, speed control, air conditioning compressor
clutch engagement and idle speed. The PCM can
adapt its programming to meet changing operating
conditions.
On XJ models, the PCM is located in the engine
compartment next to the air cleaner (Fig. 1). On YJ
models, the PCM is located in the engine compart-
ment behind the windshield washer fluid reservoir
(Fig. 2).
The PCM receives input signals from various
switches and sensors. Based on these inputs, the
PCM regulates various engine and vehicle operations
through different system components. These compo-
nents are referred to as PCM Outputs. The sensors
and switches that provide inputs to the PCM are con-
sidered PCM Inputs.The PCM adjusts ignition timing based upon in-
puts it receives from sensors that react to: engine
rpm, manifold absolute pressure, coolant tempera-
ture, throttle position, transmission gear selection
(automatic transmission), vehicle speed and the
brake switch.
The PCM adjusts idle speed based on inputs it re-
ceives from sensors that react to: throttle position,
vehicle speed, transmission gear selection, coolant
temperature and from inputs it receives from the air
conditioning clutch switch and brake switch.
Based on inputs that it receives, the PCM adjusts
ignition coil dwell. The PCM also adjusts the gener-
ator charge rate through control of the generator
field and provides speed control operation.
Powertrain Control Module (PCM) Inputs:
²Generator output
²A/C request (if equipped with factory A/C)
²A/C select (if equipped with factory A/C)
²Auto shut down (ASD) sense
²Intake air temperature sensor
²Battery voltage
²Brake switch
²Engine coolant temperature sensor
²Crankshaft position sensor
²Ignition circuit sense (ignition switch in run posi-
tion)
²Manifold absolute pressure sensor
²Overdrive/override switch
²Oxygen sensor
²Park/neutral switch (auto. trans. only)
²SCI receive (DRB scan tool connection)
²Speed control resume switch
²Speed control set switch
²Speed control on/off switch
²Camshaft position sensor signal
²Throttle position sensor
²Vehicle speed sensor
²Sensor return
²Power ground
Fig. 1 PCM LocationÐXJ Models
Fig. 2 PCM LocationÐYJ Models
14 - 18 FUEL SYSTEMJ