transmission oil JEEP CHEROKEE 1994 Service Repair Manual

ROUTINE SERVICE
The following routine vehicle service is highly rec-
ommended on a monthly basis.
TIRESÐInspect the tires for unusual wear/damage
and determine if the inflation pressure is acceptable
for the vehicle load.
BATTERYÐInspect and clean the terminals.
Tighten the terminals, if necessary.
FLUIDSÐDetermine if the coolant, brake fluid,
power steering, automatic transmission, and clutch
fluid level are acceptable. Add fluid, if necessary.
LIGHTS/ELECTRICALÐTest all the electrically
operated systems in the vehicle for proper operation.
It is also recommended that the engine oil level
and the windshield washer fluid level be deter-
mined (and corrected) during each fuel fill-up.
FUEL REQUIREMENTS
All Jeeptengines require the use of unleaded gas-
oline. In addition, the fuel must have a minimum oc-
tane rating of 87.
CAUTION: UNLEADED FUEL ONLY must be used in
vehicles equipped with a catalyst emission control
system. All vehicles have reminders printed on the
instrument panel (Fig. 1) and on the fuel filler door
(Fig. 2). Vehicles also have fuel filler tubes that are
designed to accept only the small-diameter un-
leaded gasoline nozzles. It is illegal to defeat the
design of an unleaded fuel filler tube.
CLASSIFICATION OF LUBRICANTS
Lubricating fluids and chassis component lubri-
cants are classified and graded according to stan-
dards recommended by the:
²Society of Automotive Engineers (SAE),²American Petroleum Institute (API), and
²National Lubricating Grease Institute (NLGI).
ENGINE OIL
SAE VISCOSITY GRADE
An SAE viscosity grade is used to specify viscosity
of engine oil. SAE 30 specifies a single viscosity en-
gine oil. Engine oils also have multiple viscosities
(Fig. 3).
The viscosity grade of an oil is an indicator of its
thickness or flow capability. The lower the number,
the better the flow. The second viscosity grade num-
ber (without a W suffix) is the warm/hot-temperature
viscosity. The viscosity increases with engine temper-
ature. With a single viscosity grade, the oil viscosity
is valid only for one narrow temperature range.
Fig. 1 Unleaded Fuel Only RemindersÐFuel Gauge
Fig. 2 Unleaded Fuel Only ReminderÐFuel Filler
Door
Fig. 3 SAE Oil Viscosity Grade & API Service Grade
0 - 2 LUBRICATION AND MAINTENANCEJ

MAINTENANCE SCHEDULES
INTRODUCTION
Chrysler Corporation has compiled recommended
lubrication and maintenance schedules and proce-
dures to help reduce premature wear or failure over
a broad range of operating conditions.
SEVERE SERVICE MAINTENANCE
If the vehicle is involved with a severe driving con-
dition, after each 4 800-km (3,000-miles)/3-month in-
terval. A severe driving condition includes:
²frequent short trip driving less than 24 km (15
miles);
²frequent driving in a dusty environment;
²trailer towing;
²extensive engine idling;
²sustained high-speed operation;
²desert operation;
²frequent starting and stopping;
²cold-climate operation;
²off-road driving; or
²commercial service.
MAINTENANCE SCHEDULES
AT EACH STOP FOR FUEL
²Check engine oil level, add as required.
²
Check windshield washer solvent and add if required.
ONCE A MONTH
²Check tire pressure and look for unusual wear or
damage.
²Inspect battery and clean and tighten terminals as
required.
²Check electrolyte level and add water as needed.
²Check fluid levels of coolant reservoir, power steer-
ing and transmission and add as needed.
²Check all lights and all other electrical items for
correct operation.
²Check rubber seals on each side of the radiator for
proper fit.
7,500 MILES (12 000 KM) OR AT 6 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.
15,000 MILES (24 000 KM) OR AT 12 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.²Check fluid level in battery.
²Rotate Tires.
22,500 MILES (36 000 KM) OR AT 18 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.
30,000 MILES (48 000 KM) OR AT 24 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.
37,500 MILES (60 000 KM) OR AT 30 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.
45,000 MILES (72 500 KM) OR AT 36 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.
²Check fluid level in battery.
²Rotate Tires.
52,500 MILES (84 500 KM) OR AT 42 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.
JLUBRICATION AND MAINTENANCE 0 - 5

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

PORTABLE STARTING UNIT
There are many types of portable starting units
available for starting engines. Follow the manufac-
turer's instructions when involved in any engine
starting procedure.
HOISTING RECOMMENDATIONS
FLOOR JACK
When properly positioned, a floor jack can be used
to lift a Jeeptvehicle. Support the vehicle in the
raised position with jack stands at the front and rear
ends as applicable (Fig. 7).
CAUTION: Do not attempt to lift a JeepTvehicle
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, or
²a front suspension arm.
Use the correct sub-frame rail or frame rail
lifting locations only (Fig. 7).
HOIST
A Jeeptvehicle can be lifted with a swiveling-arm
type hoist; with a wheel-lift, twin-post hoist; or with
a ramp-type, drive-on hoist.
When a swiveling-arm, frame-contact type
hoist is used, ensure that the lifting pads are po-
sitioned at the correct sub frame rail (Fig. 7).
TOWING RECOMMENDATIONS
TOWING EQUIPMENT
A vehicle equipped with SAE approved sling-type
towing equipment can be used to tow all Jeeptvehi-
cles (Fig. 8). When it is necessary to rear-tow a vehi-
cle, use the wheel-lift towing method with a tow
dolly located under the front wheels. A vehicle with
flat-bed towing equipment can also be used to trans-
port a disabled vehicle.
A wooden crossbeam with spacer blocks could pos-
sibly be required for proper connection when using
the sling-type, front-end towing method (Fig. 9).
SAFETY PRECAUTIONS
The following safety precautions must be consid-
ered when preparing for and during a vehicle towing
operation:
Fig. 7 Correct Vehicle Lifting LocationsÐTypical
Fig. 8 Tow Vehicles With Approved Equipment
Fig. 9 Crossbeam & Spacer Block Construction
0 - 8 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

DRIVETRAIN
INDEX
page page
Automatic Transmission.................... 23
Drive Shafts............................ 27
Front and Rear Axles..................... 26
Hydraulic Clutch......................... 22Manual Transmission...................... 22
Rubber and Plastic Hoses/Tubing............ 28
Transfer Case........................... 25
HYDRAULIC CLUTCH
RECOMMENDED MAINTENANCE
Check fluid level in the hydraulic clutch master
cylinder reservoir (Fig. 1) at the same time engine
oil is changed and oil filter is replaced. Add fluid as
necessary.
FLUID SPECIFICATION
The only fluid recommended for use in a hydraulic
clutch system is MOPAR Brake And Hydraulic
Clutch Fluid., or an equivalent fluid.
CAUTION: Never use reclaimed brake fluid or fluid
from an unsealed container. In addition, do not use
fluid from a container that has been opened and al-
lowed to stand for an extended length of time.
Moisture in the air can be absorbed by the fluid,
which causes dilution with loss of effectiveness.
FLUID LEVEL
Remove the master cylinder fluid reservoir cap
(Fig. 2). The fluid level is determined by its height inrelation to the level indicator ring (Fig. 3) located in-
side the reservoir. If necessary, add fluid until the
height is level with the indicator ring.
MANUAL TRANSMISSION
RECOMMENDED MAINTENANCE
The lube oil level in manual transmissions should
be determined at the same time as the engine oil is
changed and the oil filter is replaced. Add lube oil as
necessary.
Fig. 1 Hydraulic Clutch (YJ)ÐTypical
Fig. 2 Hydraulic Clutch Master Cylinder Fluid
Reservoir
Fig. 3 Hydraulic Clutch Fluid Level
0 - 22 LUBRICATION AND MAINTENANCEJ

Under normal driving conditions, manual trans-
mission lube oil should be changed after each 60
000-km (37,500 miles). With severe driving condi-
tions, after each 29 000-km (18,000 miles).
LUBRICANT SPECIFICATION
When it becomes necessary to add to or change the
lube oil in a Jeeptmanual transmission, use SAE
75W-90, API Quality Grade GL-5 gear lubricant.
LUBRICANT LEVEL
The fill-hole plug for all manual transmissions is
located on the right side of the case (Fig. 4). Deter-
mine the lubricant level according to the following
procedure.
(1) Remove the fill-hole plug (Fig. 4) from the
transmission. The lube oil should be level with the
bottom edge of the fill hole. The level can be slightly
below the bottom edge of the fill hole if the lube oil
is cold.
If the transmission is warm, lube oil could drip
out of the fill hole. This is acceptable but the
lube oil should not gush out of the fill hole.
(2) If not acceptable, raise the lube oil level to the
bottom edge of the transmission fill hole. Use SAE
75W-90, API Quality Grade GL-5 gear lubricant.
Add lube oil in small amounts to raise the
level.
(3) Install the fill-hole plug in the transmission.
Tighten the plug with 37 NIm (27 ft. lbs.) torque.
LUBE OIL CHANGE
When it becomes necessary to change manual
transmission lube oil, use the following procedure.
(1) Raise and support the vehicle.
(2) Remove the fill-hole plug from the transmis-
sion.
(3) Place a container to collect the lube oil under
the transmission drain-hole plug.(4) Remove the drain-hole plug and drain the lube
oil from the transmission into the container.
Care should be exercised when disposing used
lube oil after it has been drained from a trans-
mission.
(5) Install the drain-hole plug in the transmission.
Tighten the plug with 37 NIm (27 ft. lbs.) torque.
(6) Fill the transmission until the lube oil begins
to drip out of the fill hole with SAE 75W-90, API
Quality Grade GL-5 gear lubricant.
(7) Install the fill-hole plug in the transmission.
Tighten the plug with 37 NIm (27 ft. lbs.) torque.
(8) Remove the support and lower the vehicle.
AUTOMATIC TRANSMISSION
RECOMMENDED MAINTENANCE
Check fluid level in automatic transmissions (Fig.
5) the same time the engine oil is changed and the
oil filter is replaced. Add ATF as necessary.
Under normal driving conditions, the ATF should
be changed and the filter replaced after each 48
000-km (30,000-miles). With severe driving condi-
tions, after each 29 000-km (12,000-miles).
ATF SPECIFICATIONS
When it becomes necessary to add fluid (ATF) to a
Jeeptautomatic transmission (or when the ATF is
replaced), use:
²MerconŸ ATFonlyfor AW-4 automatic transmis-
sions (XJ vehicles), and
²MOPAR ATF PLUS type 7176 (or an equivalent
MerconŸ/Dexron IIŸ ATF) for 998 automatic trans-
missions (YJ vehicles).
SPECIAL ADDITIVES
The addition of any special-type fluid to a Jeept
automatic transmission is not recommended. The
only exception is the addition of black-light detection
Fig. 5 AW-4 Automatic Transmission (XJ)
Fig. 4 Manual Transmission Fill- & Drain-Hole
PlugsÐTypical
JLUBRICATION AND MAINTENANCE 0 - 23

DRAINING ATF/FILTER REMOVAL
Drain the automatic transmission fluid (ATF) im-
mediately after stopping the engine (before the ATF
cools).
(1) Raise and support the vehicle.
(2) Loosen the transmission pan bolts and drain
the original ATF into an appropriate container. Re-
move the pan bolts, the pan and the gasket.
Care should be exercised when disposing used
ATF after it has been drained from a vehicle
transmission.
(3) Remove the screws and the ATF filter (Fig. 8).
Discard the filter.
FILTER INSTALLATION/ATF RE-FILL
(1) Install a replacement ATF filter. Tighten the
screws with 4 NIm (35 in. lbs.) torque.
(2) Clean the pan thoroughly. Install a replace-
ment gasket on the pan. Install the pan with the at-
taching bolts:
²model AW-4 transmission Ð tighten the pan bolts
with 7 NIm (60 in. lbs.) torque; and
²model 998 transmission Ð tighten the pan bolts
with 17 NIm (150 in. lbs.) torque.
(3) Remove the support and lower the vehicle.
(4) Pour approximately 4.7 liters (5 quarts) of ATF
into the filler tube. Use MerconŸ ATF for AW-4 au-
tomatic transmissions. Use MOPAR ATF PLUS type
7176 or equivalent, for 998 automatic transmissions.
(5) Place a block in front of and at the rear of one
wheel/tire to prevent vehicle movement.
(6) Start the engine and allow it to idle a few min-
utes.
(7) Apply the brake pedal and engage the parking
brake. Move the transmission selector lever through
all positions, then place the selector lever in NEU-
TRAL position.(8) With the transmission at normal operating
temperature, observe the ATF level on the dipstick.
Add ATF (if necessary) to raise the level to the
FULL mark on the dipstick.Only 0.5 liter (1.0 pint)
will raise the level from the ADD mark to the
FULL mark when the ATF is at normal operat-
ing temperature.
(9) Inspect for fluid leaks and correct as necessary.
(10) Remove the wheel/tire blocks.
TRANSFER CASE
RECOMMENDED MAINTENANCE
The fluid (ATF) level in transfer cases should be
determined at the same time as the engine oil is
changed and the oil filter is replaced. Add ATF as
necessary.
In addition, transfer case ATF should be changed
after each 48 000-km (30,000-miles) interval of vehi-
cle operation has elapsed.
FLUID SPECIFICATIONS
If it is necessary to add fluid to a transfer case (or
when the fluid is changed), use MOPAR ATF PLUS
type 7176 or an equivalent MerconŸ/Dexron IIŸ
ATF.
FLUID LEVEL
The transfer case fill-hole plug is located at the
rear of the housing (Fig. 9).
Determine the transfer case fluid (ATF) level ac-
cording to the following procedure.
(1) Raise and support the vehicle.
(2) Remove the fill-hole plug from the transfer
case. The ATF level should be at the bottom edge of
the fill hole. The level can be slightly below the bot-
tom edge of the fill hole if the fluid is cold.
Fig. 9 Transfer CaseÐTypical
Fig. 8 ATF FilterÐTypical
JLUBRICATION AND MAINTENANCE 0 - 25

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