ABS JEEP CHEROKEE 1995 Service Manual PDF

PARKING BRAKE REAR CABLE REPLACEMENT (YJ)
(1) Raise vehicle and loosen equalizer nuts (Fig.
17).
(2) Remove clamp and cotter pin attaching rear ca-
ble to equalizer and remove cable.
(3) Remove cable clips.
(4) Remove rear wheel and brake drum.
(5) Remove secondary brakeshoe and disconnect
cable from lever on brakeshoe.
(6) Compress cable retainer with hose clamp (Fig.
16) and remove cable from backing plate.
(7) Install new cable in backing plate. Be sure ca-
ble retainer lock tabs are engaged in plate.
(8) Install secondary brakeshoe.
(9) Adjust brakeshoes to brake drum and install
drum and wheel.
(10) Install cable in equalizer. Secure cable with
retainer and cotter pin.
(11) Install cable clips.
(12) Adjust parking brakes. Refer to procedure in
this section.
PARKING BRAKE SWITCH
The parking brake switch is located on the lever
assembly on XJ models, or on the foot pedal assem-
bly on YJ models (Fig. 18). Switch replacement is de-
scribed in the parking brake lever or foot pedal
removal/installation procedures in this section.
Fig. 17 Parking Brake Components (YJ)
Fig. 18 Parking Brake Switch Location
5 - 68 PARKING BRAKESJ

COOLANT
GENERAL INFORMATION
The cooling system is designed around the coolant.
Coolant flows through the engine water jackets ab-
sorbing heat produced during engine operation. The
coolant carries heat to the radiator and heater core.
Here it is transferred to the ambient air passing
through the radiator and heater core fins. The cool-
ant also removes heat from the automatic transmis-
sion fluid in vehicles equipped with an automatic
transmission.
COOLANT PERFORMANCE
The required ethylene-glycol (antifreeze) and water
mixture depends upon climate and vehicle operating
conditions. The coolant performance of various mix-
tures follows:
Pure Water-Water can absorb more heat than a
mixture of water and ethylene-glycol. This is for pur-
pose of heat transfer only. Water also freezes at a
higher temperature and allows corrosion.
100 percent Ethylene-Glycol-The corrosion in-
hibiting additives in ethylene-glycol need the pres-
ence of water to dissolve. Without water, additives
form deposits in system. These act as insulation
causing temperature to rise to as high as 149ÉC
(300ÉF). This temperature is hot enough to melt plas-
tic and soften solder. The increased temperature can
result in engine detonation. In addition, 100 percent
ethylene-glycol freezes at -22ÉC (-8ÉF).
50/50 Ethylene-Glycol and Water-Is the recom-
mended mixture, it provides protection against freez-
ing to -37ÉC (-35ÉF). The antifreeze concentration
must alwaysbe a minimum of 44 percent, year-
round in all climates. If percentage is lower, engine
parts may be eroded by cavitation. Maximum protec-
tion against freezing is provided with a 68 percent
antifreeze concentration, which prevents freezing
down to -67.7ÉC (-90ÉF). A higher percentage will
freeze at a warmer temperature. Also, a higher per-
centage of antifreeze can cause the engine to over-
heat because specific heat of antifreeze is lower than
that of water.
CAUTION: Richer antifreeze mixtures cannot be
measured with normal field equipment and can
cause problems associated with 100 percent ethyl-
ene-glycol.
COOLANT SELECTION-ADDITIVES
Coolant should be maintained at the specified level
with a mixture of ethylene glycol-based antifreeze
and low mineral content water. Only use an anti-
freeze containing ALUGARD 340-2 Ÿ.CAUTION: Do not use coolant additives that are
claimed to improve engine cooling.
COOLANT SERVICE
It is recommended that the cooling system be
drained and flushed at 84,000 kilometers (52,500
miles), or 3 years, whichever occurs first. Then every
two years, or 48,000 kilometers (30,000 miles),
whichever occurs first.
COOLANT LEVEL CHECKÐROUTINE
Do not remove radiator cap for routine cool-
ant level inspections. The coolant level can be
checked at coolant reserve/overflow tank.
The coolant reserve/overflow system provides a
quick visual method for determining coolant level
without removing radiator pressure cap. With engine
idling and at normal operating temperature, observe
coolant level in reserve/overflow tank. The coolant
level should be between ADD and FULL marks.
ADDING ADDITIONAL COOLANTÐROUTINE
Do not remove radiator cap to add coolant to
system.When adding coolant to maintain correct
level, do so at coolant reserve/overflow tank. Use a
50/50 mixture of ethylene-glycol antifreeze containing
Alugard 340-2 Ÿ and low mineral content water. Re-
move radiator cap only for testing or when refilling
system after service. Removing cap unnecessarily can
cause loss of coolant and allow air to enter system,
which produces corrosion.
COOLANT LEVEL CHECK-SERVICE
The cooling system is closed and designed to main-
tain coolant level to top of radiator.
WARNING: DO NOT OPEN RADIATOR DRAINCOCK
WITH ENGINE RUNNING OR WHILE ENGINE IS HOT
AND COOLING SYSTEM IS UNDER PRESSURE.
When vehicle servicing requires a coolant level
check in radiator, drain several ounces of coolant
from radiator drain cock. Do this while observing
coolant reserve/overflow system tank. The coolant
level in reserve/overflow tank should drop slightly. If
not, inspect for a leak between radiator and coolant
reserve/overflow system connection. Remove radiator
cap. The coolant level should be to top of radiator. If
not and if coolant level in reserve/overflow tank is at
ADD mark, check for:
²An air leak in coolant reserve/overflow tank or its
hose
²An air leak in radiator filler neck
²Leak in pressure cap seal to radiator filler neck
LOW COOLANT LEVEL-AERATION
If the coolant level in radiator drops below top of
radiator core tubes, air will enter cooling system.
7 - 20 COOLING SYSTEM SERVICE PROCEDURESJ

WARNING: HOT, PRESSURIZED COOLANT CAN
CAUSE INJURY BY SCALDING.
Carefully remove the radiator pressure cap from
the filler neck and check the coolant level. Push
down on the cap to disengage it from the stop tabs.
Wipe the inner part of the filler neck and examine
the lower inside sealing seat for nicks, cracks, paint,
dirt and solder residue. Inspect the reserve/overflow
tank tube for internal obstructions. Insert a wire
through the tube to be sure it is not obstructed.
Inspect the cams on the outside part of the filler
neck. If the cams are bent, seating of pressure cap
valve and tester seal will be affected. Replace cap if
cams are bent.
Attach pressure tester 7700 (or an equivalent) to
the radiator filler neck (Fig. 21).Operate the tester pump to apply 124 kPa (18 psi)
pressure to the system. If the hoses enlarge exces-
sively or bulge while testing, replace as necessary.
Observe the gauge pointer and determine the condi-
tion of the cooling system according to the following
criteria:
²Holds Steady: If the pointer remains steady for
two minutes, there are no serious coolant leaks in
the system. However, there could be an internal leak
that does not appear with normal system test pres-
sure. Inspect for interior leakage or do the Internal
Leakage Test. Do this if it is certain that coolant is
being lost and no leaks can be detected.
²Drops Slowly: Shows a small leak or seepage is oc-
curring. Examine all connections for seepage or slight
leakage with a flashlight. Inspect the radiator, hoses,
gasket edges and heater. Seal any small leak holes
with a Sealer Lubricant or equivalent. Repair leak
holes and reinspect the system with pressure ap-
plied.
²Drops Quickly: Shows that a serious leakage is oc-
curring. Examine the system for serious external
leakage. If no leaks are visible, inspect for internal
leakage. Large radiator leak holes should be repaired
by a reputable radiator repair shop.
INTERNAL LEAKAGE INSPECTION
Remove the engine oil pan drain plug and drain a
small amount of engine oil. Coolant, being heavier
than engine oil, will drain first. Another way of test-
ing is to operate the engine and check for water glob-
ules on the engine oil dipstick. Also inspect the
automatic transmission oil dipstick for water glob-
ules. Inspect the automatic transmission fluid cooler
for leakage. Operate the engine without the pressure
cap on the radiator until thermostat opens.
Attach a pressure tester to the filler neck. If pres-
sure builds up quickly, a leak exists as a result of a
faulty cylinder head gasket or crack in the engine.
Repair as necessary.
WARNING: DO NOT ALLOW PRESSURE TO EX-
CEED 124 KPA (18 PSI). TURN THE ENGINE OFF.
TO RELEASE THE PRESSURE, ROCK THE TESTER
FROM SIDE TO SIDE. WHEN REMOVING THE
TESTER, DO NOT TURN THE TESTER MORE THAN
1/2 TURN IF THE SYSTEM IS UNDER PRESSURE.
If there is no immediate pressure increase, pump
the pressure tester until the indicated pressure is
within the system range. Vibration of the gauge
pointer indicates compression or combustion leakage
into the cooling system.
WARNING: DO NOT DISCONNECT THE SPARK
PLUG WIRES WHILE THE ENGINE IS OPERATING.
Fig. 20 Leak Detection Using Black LightÐTypical
Fig. 21 Pressurizing SystemÐTypical
JCOOLING SYSTEM SERVICE PROCEDURES 7 - 23

CAUTION: Do not operate the engine with a spark
plug shorted for more than a minute. The catalytic
converter may be damaged.
Isolate the compression leak by shorting each
spark plug to the cylinder block. The gauge pointer
should stop or decrease vibration when spark plug
for leaking cylinder is shorted. This happens because
of the absence of combustion pressure.
COMBUSTION LEAKAGE TEST (WITHOUT
PRESSURE TESTER)
DO NOT WASTE reusable coolant. If the solution
is clean, drain the coolant into a clean container for
reuse.
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND UNDER
PRESSURE. SERIOUS BURNS FROM COOLANT
CAN OCCUR.
Drain sufficient coolant to allow for thermostat re-
moval. Refer to Thermostat Replacement. Disconnect
the water pump drive belt.
Disconnect the upper radiator hose from the ther-
mostat housing. Remove the housing and thermostat.
Install the thermostat housing.
Add coolant to the radiator to bring the level to
within 6.3 mm (1/4 in) of the top of the thermostat
housing.
CAUTION: Avoid overheating. Do not operate the
engine for an excessive period of time. Open the
draincock immediately after the test to eliminate
boil over of coolant.
Start the engine and accelerate rapidly three times
(to approximately 3000 rpm) while observing the
coolant. If internal engine combustion gases are leak-
ing into the cooling system, bubbles will appear in
the coolant. If bubbles do not appear, there is no in-
ternal combustion gas leakage.
COOLANT RESERVE/OVERFLOW SYSTEM
The system works along with the radiator pressure
cap. This is done by using thermal expansion and
contraction of the coolant to keep the coolant free of
trapped air. It provides:
²A volume for coolant expansion and contraction.
²A convenient and safe method for checking/adjust-
ing coolant level at atmospheric pressure. This is
done without removing the radiator pressure cap.
²Some reserve coolant to the radiator to cover mi-
nor leaks and evaporation or boiling losses.
As the engine cools, a vacuum is formed in the
cooling system of both the radiator and engine. Cool-ant will then be drawn from the coolant tank and re-
turned to a proper level in the radiator.
The coolant reserve/overflow system consists of a
radiator mounted pressurized cap, a plastic reserve/
overflow tank (Figs. 22, 23 or 24), a tube (hose) con-
necting the radiator and tank, and an overflow tube
on the side of the tank.
Fig. 22 Reserve/Overflow TankÐYJ Models
Fig. 23 Reserve/Overflow TankÐXJ ModelsÐExcept
Right Hand Drive
7 - 24 COOLING SYSTEM SERVICE PROCEDURESJ

(4) For access to radiator draincock, remove radia-
tor grille mounting screws and remove grill. Refer to
Group 23, Body for procedures.
(5) Attach one end of a 24 inch long X 1/4 inch ID
hose to the radiator draincock. Put the other end into
a clean container. Open draincock and drain radiator.
(6) If equipped, disconnect auxiliary electric cooling
fan electrical connector (Fig. 31).
(7) If equipped, remove two electric cooling fan
mounting bolts. Lift cooling fan straight up until
alignment tabs at the bottom are clear of slots in
bracket at bottom of radiator (Fig. 32).
(8) Remove the two mechanical (non-electrical) fan
shroud mounting bolts. Lift shroud straight up until
alignment tabs at the bottom are clear of slots in
bracket at bottom of radiator (Fig. 32). Place shroud
over mechanical fan.
(9) If equipped, disconnect and plug automatic
transmission fluid cooler lines. Refer to Group 21,
Transmissions for procedures. If equipped with re-
mote transmission cooler, remove line to cooler from
bracket at bottom of radiator.
(10) Disconnect radiator upper and lower hoses
clamps (Figs. 27 and 28). Disconnect radiator upper
and lower hoses.
(11) Mark the position of the hood latch striker on
the radiator crossmember and remove hood latch
striker.(12) Remove two radiator upper crossmember-to-
isolator nuts (Fig. 32).
Fig. 31 Auxiliary Electric Cooling Fan Wiring
ConnectorÐTypical
Fig. 32 Auxiliary Electric Cooling Fan and Fan ShroudÐTypical
JCOOLING SYSTEM SERVICE PROCEDURES 7 - 29

(13) Remove four radiator upper crossmember
bolts (Fig. 32) and remove upper crossmember.
(14) If equipped with air conditioning, separate ra-
diator from condenser by removing condenser-to-radi-
ator mounting brackets (Fig. 33).
(15) Lift radiator straight up and out of engine
compartment taking care not to damage fins.
INSTALLATION
The radiator is supplied with two alignment dowels
(Figs. 32 or 34). They are located on the bottom tank
and fit into rubber grommets in the radiator lower
crossmember.
(1) Lower radiator into engine compartment. Posi-
tion alignment dowels into rubber grommets in radi-
ator lower crossmember (Figs. 32 or 34).
(2) If equipped with air conditioning, attach con-
denser to radiator with mounting brackets (Fig. 33).
(3) Install radiator upper crossmember and four
mounting bolts.
(4) Install radiator upper crossmember-to-isolator
nuts. Tighten nuts to 10 Nzm (86 in. lbs.) torque. If
isolator-to-radiator nuts had been removed, tighten
them to 5 Nzm (47 in. lbs.) torque.
(5) Install hood latch striker. Note previously
marked position.
(6) Connect radiator upper and lower hoses.
(7) If equipped, connect automatic transmission
fluid cooler lines. Refer to Group 21, Transmissions
for procedures. If equipped with remote cooler, attach
cooler line to bracket at bottom of radiator.
(8) Install electric cooling fan (if equipped). Insert
alignment tabs at bottom of fan shroud into slots inbracket at bottom of radiator. Tighten mounting bolts
to3Nzm (31 in. lbs.) torque.
(9) Connect electric cooling fan electrical connector.
(10) Install mechanical cooling fan shroud. Insert
alignment tabs at bottom of shroud into slots in
bracket at bottom of radiator. Tighten mounting bolts
to3Nzm (31 in. lbs.) torque.
(11) Close radiator draincock.
(12) Install grille.
(13) Connect negative battery cable.
(14) Fill cooling system with correct coolant. Refer
to the Coolant section of this group.
(15) Install pressure cap.
(16) Check and adjust automatic transmission
fluid level (if equipped).
YJ MODELS
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND PRES-
SURIZED. SERIOUS BURNS FROM THE COOLANT
CAN OCCUR.
DO NOT WASTE reusable coolant. If solution is
clean, drain coolant into a clean container for reuse.
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. 27). SNAP-ON CLAMP TOOL (NUMBER
HPC-20) MAY BE USED FOR LARGER CLAMPS. AL-
Fig. 33 Condenser-to-Radiator Mounting BracketsÐ
XJ with 4.0L 6- Cylinder Engine
Fig. 34 Radiator InstallationÐXJ Models with 4.0L
6-Cylinder Engine
7 - 30 COOLING SYSTEM SERVICE PROCEDURESJ

nostic Procedures manual for diagnostic information
and operation of the DRB scan tool.
To test operation of the fan relay only, refer to Re-
laysÐOperation/Testing. This can be found in Group
14, Fuel Systems.
REMOVAL
The auxiliary cooling fan is attached to the radia-
tor upper crossmember behind the radiator.
(1) Remove the two fan mounting bolts from radi-
ator upper crossmember (Fig. 43).
(2) Disconnect the electric fan connector.
(3) Lift fan straight up and out of vehicle.
INSTALLATION
(1) Align lower retaining tabs of fan shroud with
slots in bracket at bottom of radiator. Push fan down
into position.
(2) Tighten the mounting bolts to 4 Nzm (31 in.
lbs.) torque.
(3) Connect auxiliary cooling fan electrical connec-
tor.
TRANSMISSION OIL COOLERS
WATER-TO-OIL COOLER
All models equipped with an automatic transmis-
sion are equipped with a transmission oil cooler
mounted internally within the radiator tank. This in-
ternal cooler is supplied as standard equipment on
all models equipped with an automatic transmission.
Transmission oil is cooled when it passes through
this separate cooler. In case of a leak in the internalradiator mounted transmission oil cooler, engine cool-
ant may become mixed with transmission fluid or
transmission fluid may enter engine cooling system.
Both cooling system and transmission should be
drained and inspected if the internal radiator
mounted transmission cooler is leaking.
Also refer to the section on Transmission Air-to-Oil
Coolers. This auxiliary air-to-oil cooler is an option
on most engine packages.
REPLACING WATER-TO-OIL COOLER IN
RADIATOR SIDE TANK
The internal transmission oil cooler located within
the radiator is not serviceable. If it requires service,
the radiator must be replaced.
Once the repaired or replacement radiator has
been installed, fill the cooling system and inspect for
leaks. Refer to the Refilling Cooling System and Test-
ing Cooling System For Leaks sections in this group.
If the transmission operates properly after repairing
the leak, drain the transmission and remove the
transmission oil pan. Inspect for sludge and/or rust.
Inspect for a dirty or plugged inlet filter. If none of
these conditions are found, the transmission and
torque convertor may not require reconditioning. Re-
fer to Group 21 for automatic transmission servicing.
AIR-TO-OIL COOLER
An auxiliary air-to-oil transmission oil cooler is
available with most engine packages.
On XJ and YJ models, the cooler is located in front
of the radiator or A/C condenser (if equipped) and be-
hind the grill (Figs. 44, 45 or 46). It is mounted to
the front frame crossmember.
Fig. 43 Auxiliary Cooling FanÐRemove/InstallÐ
Typical
Fig. 44 Auxiliary Air-To-Oil CoolerÐYJ Models
7 - 36 COOLING SYSTEM SERVICE PROCEDURESJ

BATTERY
GENERAL INFORMATION
The storage battery is a device used to store elec-
trical energy potential in a chemical form. When an
electrical load is applied to the battery terminals, an
electrochemical reaction occurs within the battery.
This reaction causes the battery to discharge electri-
cal current.
The battery is made up of 6 individual cells that
are connected in series. Each cell contains positively
charged plate groups made of lead oxide, and nega-
tively charged plate groups made of sponge lead.
These dissimilar metal plates are submerged in a
sulfuric acid and water solution called electrolyte.
As the battery discharges, a gradual chemical
change takes place within each cell. The sulfuric acid
in the electrolyte combines with the plate materials,
causing both plates to change to lead sulfate. At the
same time, oxygen from the positive plate material
combines with hydrogen from the sulfuric acid, caus-
ing the electrolyte to become mainly water.
The chemical changes within the battery are
caused by movement of excess or free electrons be-
tween the positive and negative plate groups. Thismovement of electrons produces a flow of electrical
current through the load device attached to the bat-
tery terminals.
As the plate materials become more similar chem-
ically, and the electrolyte becomes less acid, the volt-
age potential of each cell is reduced. However, by
charging the battery with a voltage higher than that
of the battery, the process is reversed.
Charging the battery gradually changes the sul-
fated lead plates back into sponge lead and lead ox-
ide, and the water back into sulfuric acid. This action
restores the difference in electron charges deposited
on the plates, and the voltage potential of the battery
cells.
For a battery to remain useful, it must be able to
produce high-amperage current over an extended pe-
riod. A battery must also be able to accept a charge,
so that its voltage potential may be restored.
In addition to producing and storing electrical en-
ergy, the battery serves as a capacitor or voltage sta-
bilizer for the vehicle electrical system. It absorbs
abnormal or transient voltages caused by switching
of any of the vehicle's electrical components.
The battery is vented to release excess gas that is
created when the battery is being charged or dis-
Fig. 1 Starting System Components (Typical)
Fig. 2 Charging System Components (Typical)
8A - 2 BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICSJ

IGNITION SYSTEMS
CONTENTS
page page
COMPONENT IDENTIFICATION/SYSTEM
OPERATION........................... 1
COMPONENT REMOVAL/INSTALLATION...... 17
DIAGNOSTICS/SERVICE PROCEDURES....... 6IGNITION SWITCHÐXJ MODELS........... 26
IGNITION SWITCHÐYJ MODELS........... 29
SPECIFICATIONS........................ 32
COMPONENT IDENTIFICATION/SYSTEM OPERATION
INDEX
page page
Automatic Shutdown (ASD) Relay.............. 1
Camshaft Position Sensor.................... 2
Crankshaft Position Sensor................... 3
Distributors............................... 4
Engine Coolant Temperature Sensor............ 5
General Information........................ 1Ignition Coil.............................. 4
Intake Manifold Air Temperature Sensor.......... 5
Manifold Absolute Pressure (MAP) Sensor........ 5
Oxygen (O2S) Sensor....................... 5
Powertrain Control Module (PCM).............. 5
Throttle Position Sensor..................... 5
GENERAL INFORMATION
Throughout this group, references are made to par-
ticular vehicle models by alphabetical designation
(XJ or YJ) or by the particular vehicle nameplate. A
chart showing a breakdown of alphabetical designa-
tions is included in the Introduction group at the be-
ginning of this manual.
This section of the group, Component Identifica-
tion/System Operation, will discuss ignition system
operation and will identify ignition system compo-
nents.
For diagnostic procedures and adjustments, refer to
the Diagnostics/Service Procedures section of this
group.
For removal and installation of ignition system
components, refer to the Component Removal/Instal-
lation section of this group.
For other useful information, refer to On-Board Di-
agnostics in the General Diagnosis sections of Group
14, Fuel System in this manual.
For operation of the DRB Scan Tool, refer to the
appropriate Powertrain Diagnostic Procedures ser-
vice manual.
An Ignition specifications section is included at the
end of this group. A general Maintenance Schedule
(mileage intervals) for ignition related items can be
found in Group 0, Lubrication and Maintenance. This
schedule can also be found in the Owners Manual.
IGNITION SYSTEMS
A multi-port, fuel injected engine is used on all
models. The ignition system is controlled by the pow-
ertrain control module (PCM) on all engines. The
PCM was formerly referred to as the SBEC or engine
controller.
The ignition system consists of:
²Spark plugs
²Ignition coil
²Secondary ignition cables
²Distributor (contains rotor and camshaft position
sensor)
²Powertrain control module (PCM)
²Crankshaft position sensor
AUTOMATIC SHUTDOWN (ASD) RELAY
The automatic shutdown (ASD) relay is located in
the power distribution center (PDC) near the battery
(Fig. 1 or 2). As one of its functions, it will supply
battery voltage to the ignition coil.
The ground circuit for the ASD relay is controlled
by the powertrain control module (PCM). This is
done through pin/cavity number 51 of the PCM 60-
way connector. The PCM then regulates ASD relay
operation by switching this ground circuit on-and-off.
Also refer to Ignition Coil for additional informa-
tion.
JIGNITION SYSTEMS 8D - 1

On the 4.0L 6-cylinder engine, the ignition coil is
mounted to a bracket on the side of the engine (to
the front of the distributor) (Fig. 11).
For component testing, refer to the Diagnostics/Ser-
vice Procedures section of this group.
For removal and installation of this component, re-
fer to the Component Removal/Installation section of
this group.
ENGINE COOLANT TEMPERATURE SENSOR
For an operational description, diagnosis and re-
moval/installation procedures, refer to Group 14,
Fuel System.
INTAKE MANIFOLD AIR TEMPERATURE SENSOR
For an operational description, diagnosis or remov-
al/ installation procedures, refer to Group 14, Fuel
Systems.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
For an operational description, diagnosis and re-
moval/installation procedures, refer to Group 14,
Fuel System.
POWERTRAIN CONTROL MODULE (PCM)
The PCM was formerly referred to as the SBEC or
engine controller. On XJ models, the PCM is located
in the engine compartment next to the air cleaner
(Fig. 12). On YJ models, the PCM is located in the
engine compartment behind the windshield washer
fluid reservoir (Fig. 13).
The ignition system is controlled by the PCM.
Base ignition timing by rotation of distributor
is not adjustable.The PCM opens and closes the ig-
nition coil ground circuit to operate the ignition coil.
This is done to adjust ignition timing, both initial
(base) and advance, for changing engine operating
conditions.The amount of electronic spark advance provided
by the PCM is determined by five input factors: En-
gine coolant temperature, engine rpm, intake mani-
fold air temperature, intake manifold absolute
pressure and throttle position.
For removal and installation of this component, re-
fer to the Component Removal/Installation section of
this group.
For PCM diagnostics, refer to the appropriate Pow-
ertrain Diagnostic Procedures service manual for op-
eration of the DRB scan tool.
THROTTLE POSITION SENSOR
For an operational description, diagnosis and re-
moval/installation procedures, refer to Group 14,
Fuel System.
OXYGEN (O2S) SENSOR
For an operational description, diagnosis and re-
moval/installation procedures, refer to Group 14,
Fuel System.
Fig. 11 Ignition CoilÐTypical
Fig. 12 PCM LocationÐXJ Models
Fig. 13 PCM LocationÐYJ Models
JIGNITION SYSTEMS 8D - 5