1995 JEEP YJ Fuel system

To test ignition coil-to-distributor cap cable, do not
remove the cable from the cap. Connect ohmmeter to
rotor button (center contact) of distributor cap and
terminal at ignition coil end of cable. If resistance is
not within specifications as found in the Spark Plug
Cable Resistance chart, remove the cable from the
distributor cap. Connect the ohmmeter to the termi-
nal ends of the cable. If resistance is not within spec-
ifications as found in the Spark Plug Cable
Resistance chart, replace the cable. Inspect the igni-
tion coil tower for cracks, burns or corrosion.
For removal and installation of spark plug cables,
refer to Spark Plug Secondary Cables in the Compo-
nent Removal/Installation section.
THROTTLE POSITION SENSOR TEST
For an operational description, diagnosis and re-
moval/installation procedures, refer to Group 14,
Fuel System.
OXYGEN (O2S) SENSOR TESTS
For an operational description, diagnosis or remov-
al/ installation procedures, refer to Group 14, Fuel
Systems.
ON-BOARD DIAGNOSTICS
FOR CERTAIN IGNITION SYSTEM
COMPONENTS
The powertrain control module (PCM) performs an
On-Board Diagnostic (OBD) check for certain ignition
system components on all vehicles. This is done by
setting a diagnostic trouble code (DTC).
A DTC can be obtained in two different ways. One
of the ways is by connecting the DRB scan tool to the
data link connector. This connector is located in the
engine compartment (Figs. 26 or 27). Refer to the ap-
propriate Powertrain Diagnostic Procedures service
manual for operation of the DRB scan tool. The other
way is to cycle the ignition key and observe the mal-
function indicator lamp (MIL). The MIL lamp is dis-
played on the instrument panel as the CHECK
ENGINE lamp (Figs. 28 or 29). This lamp will flash
a numeric code. If a numeric code number 11 (for the
crankshaft position sensor) or 42 (for the ASD relay)
is observed, a problem has been found in the ignition
system.
Note that the CHECK ENGINE lamp will illumi-
nate initially for approximately two seconds each
time the ignition key is turned to the ON position.
This is done for a bulb test.
Fig. 26 Data Link ConnectorÐXJ ModelsÐTypical
Fig. 27 Data Link ConnectorÐYJ ModelsÐTypical
JIGNITION SYSTEMS 8D - 15

For a complete operational description of all
DTC's, for accessing a DTC and for erasing aDTC, refer to On-Board Diagnostics. This can
be found in the General Diagnosis sections of
Group 14, Fuel System. For numeric flash lamp
code charts, refer to Diagnostic Trouble Code
(DTC). This can also be found in the General
Diagnosis sections of Group 14, Fuel System.
Fig. 28 Check Engine LampÐXJ ModelsÐTypicalFig. 29 Check Engine LampÐYJ ModelsÐTypical
8D - 16 IGNITION SYSTEMSJ

transmission bellhousing at the left/rear side of the
engine block (Figs. 4, 5 or 6).
On all 2.5L 4-cylinder and 4.0L 6-cylinder engines
(except YJ models with an automatic transmission
and 4.0L 6-cylinder engine) the sensor is attached
with two bolts. The 2.5L 4-cylinder engine, when
equipped with an automatic transmission, will have
the sensor mounted with two nuts.
On YJ models with a 4.0L 6-cylinder engine and
automatic transmission, the sensor is attached with a
single bolt (Fig. 6).
REMOVALÐALL ENGINES
(1) Near the rear of the intake manifold, discon-
nect the pigtail harness (on the sensor) from the
main electrical harness.
(2) Remove the nut holding sensor wire clip to fuel
rail mounting stud.
(3) Depending upon application, remove either the
sensor mounting bolt(s) or nuts.
(4) Remove the sensor.(5) Remove clip from sensor wire harness.
INSTALLATIONÐALL EXCEPT YJ MODELS
WITH 4.0L 6-CYLINDER ENGINE AND
AUTOMATIC TRANSMISSION
(1) Install the sensor flush against the opening in
the transmission housing.
(2) Install and tighten the two sensor mounting
bolts (or nuts) to 19 Nzm (14 ft. lbs.) torque.
Fig. 3 Camshaft Position Sensor
Fig. 4 Crankshaft Position SensorÐ2.5L 4-Cylinder
EngineÐTypical
Fig. 5 Crankshaft Position SensorÐ4.0L 6-Cylinder
EngineÐAll Except YJ models With Automatic
Transmission
Fig. 6 Crankshaft Position SensorÐ4.0L 6-Cylinder
EngineÐYJ models With Automatic Transmission
8D - 18 IGNITION SYSTEMSJ

CAUTION: On some models, two bolts are used to
secure the sensor to the transmission. These bolts
are specially machined to correctly space the unit
to the flywheel. Do not attempt to install any other
bolts.
(3) Connect the electrical connector to the sensor.
(4) Install clip on sensor wire harness.
(5) Install clip over fuel rail mounting stud. Install
clip mounting nut.
INSTALLATIONÐYJ MODELS WITH 4.0L
6-CYLINDER ENGINE AND AUTOMATIC
TRANSMISSION
(1) Install the sensor into the access hole on the
transmission.
(2) Install sensor mounting bolt (Fig. 6).
(3) Tighten sensor mounting bolt to 6-to-8 Nzm (50-
to-70 in. lbs.) torque.
(4) Connect the electrical connector to sensor.
(5) Install the clip to sensor wire harness.
(6) Install clip over fuel rail mounting stud. Install
clip mounting nut.
ENGINE COOLANT TEMPERATURE SENSOR
For an operational description, diagnosis and re-
moval/installation procedures, refer to Group 14,
Fuel System.
DISTRIBUTOR
GENERAL INFORMATION
All distributors contain an internal oil seal that
prevents oil from entering the distributor housing.
The seal is not serviceable.
Factory replacement distributors are equipped with
a plastic alignment pin already installed. The pin is
located in an access hole on the bottom of the distrib-
utor housing (Fig. 7). It is used to temporarily lock
the rotor to the cylinder number 1 position during in-
stallation. The pin must be removed after installing
the distributor.
The camshaft position sensor is located in the dis-
tributor on all engines (Fig. 8). For removal/installa-
tion procedures, refer to Camshaft Position Sensor.
Distributor removal is not necessary for sensor re-
moval.
Refer to figure 8 for an exploded view of the dis-
tributor.
A fork with a slot is supplied on the bottom of the
distributor housing where the housing base seats
against the engine block (Fig. 8). The centerline of
the slot aligns with the distributor holddown bolt
hole in the engine block. Because of the fork, the dis-
tributor cannot be rotated. Distributor rotation is not
necessary as all ignition timing requirements are
handled by the powertrain control module (PCM).The position of the distributor determines fuel syn-
chronization only. It does not determine ignition tim-
ing.
Do not attempt to modify this fork to attain
ignition timing.
Fig. 7 Plastic Alignment Pin
Fig. 8 DistributorÐ2.5L Or 4.0L EnginesÐTypical
JIGNITION SYSTEMS 8D - 19

(3) Remove ignition coil mounting bolts (nuts are
used on back side of bracket). Remove coil.
INSTALLATION
(1) Install ignition coil to bracket on cylinder block
with mounting bolts and nuts.
(2) Connect engine harness connector to coil.
(3) Connect ignition coil cable to ignition coil.
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.
OXYGEN (O2S) SENSOR
For an operational description, diagnosis or remov-
al/ installation procedures, refer to Group 14, Fuel
Systems.
POWERTRAIN CONTROL MODULE (PCM)
The PCM was formerly referred to as the SBEC or
engine controller.
XJ MODELS
On XJ models, the PCM is located in the engine
compartment next to the air cleaner (Fig. 17).
REMOVAL
(1) Disconnect negative battery cable at battery.
(2) Loosen 60-way connector mounting screw until
connector can be disengaged from PCM.
(3) Pull 60-way connector straight back from PCM.
(4) Remove PCM mounting bolts.
(5) Remove PCM from vehicle.INSTALLATION
(1) Check the pins in the PCM 60-way electrical
connector for damage. Repair as necessary.
(2) Install PCM. Tighten mounting bolts to 1 Nzm
(9 in. lbs.) torque.
(3) Engage 60-way connector into PCM. Tighten
connector mounting screw to 4 Nzm (35 in. lbs.)
torque.
(4) Connect battery cable to battery.
YJ MODELS
On YJ models, the PCM is located in the engine
compartment behind the windshield washer fluid res-
ervoir (Fig. 18).
REMOVAL
(1) Disconnect negative battery cable at battery.
(2) Remove windshield washer fluid reservoir.
(3) Loosen 60-way connector mounting screw until
connector can be disengaged from PCM.
(4) Pull 60-way connector straight back from PCM.
(5) Remove PCM mounting bolts.
(6) Remove PCM from vehicle.
INSTALLATION
(1) Check the pins in the PCM 60-way electrical
connector for damage. Repair as necessary.
(2) Install PCM. Tighten mounting bolts to 1 Nzm
(9 in. lbs.) torque.
(3) Engage 60-way connector into PCM. Tighten
connector mounting screw to 4 Nzm (35 in. lbs.)
torque.
(4) Connect battery cable to battery.
(5) Install washer fluid reservoir.
SPARK PLUGS
PLUG REMOVAL
(1) Always remove spark plug or ignition coil ca-
bles by grasping at the cable boot (Fig. 19). Turn the
cable boot 1/2 turn and pull straight back in a steady
Fig. 17 PCM LocationÐXJ Models
Fig. 18 PCM LocationÐYJ Models
JIGNITION SYSTEMS 8D - 23

When installing new cables, make sure a positive
connection is made. A snap should be felt when a
good connection is made between the plug cable and
the distributor cap tower.THROTTLE POSITION SENSOR (TPS)
For an operational description, diagnosis and re-
moval/installation procedures, refer to Group 14,
Fuel System.
Fig. 22 Engine Firing OrderÐ4.0L 6-Cylinder EngineFig. 21 Engine Firing OrderÐ2.5L 4-Cylinder Engine
JIGNITION SYSTEMS 8D - 25

INSTRUMENT PANEL AND GAUGES
GROUP INDEX
INSTRUMENT PANEL AND GAUGESÐXJ...... 1INSTRUMENT PANEL AND GAUGESÐYJ..... 24
INSTRUMENT PANEL AND GAUGESÐXJ
CONTENTS
page page
DIAGNOSIS............................. 5
GENERAL INFORMATION.................. 1SERVICE PROCEDURES.................. 17
SPECIFICATIONS........................ 23
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
or heater and air conditioning components can be ac-
cessed without complete instrument panel removal. If
necessary, the instrument panel can be rolled-down
and removed from the vehicle as an assembly.
Removal of the instrument cluster bezel allows ac-
cess to the cluster assembly, most switches, the cli-
mate controls, and the radio. Removal of the cluster
assembly allows access to the individual gauges, illu-
mination and indicator lamp bulbs, printed circuits,
and most wiring.
Removal of the lower instrument panel allows ac-
cess to heater and air conditioning components, the
fuseblock module, the relay center, and other wiring
and electrical components. Those models equipped
with a driver's-side airbag restraint have a knee
blocker and reinforcement behind the driver's-side
lower instrument panel.
The instrument panel layout is mirror image for
left-hand and right-hand drive vehicles. In most
cases, the diagnosis and service procedures found in
this group are applicable to either vehicle. Although,most illustrations represent only the typical left-hand
drive version. Exceptions are clearly identified as
Right-Hand Drive (RHD).
INSTRUMENT CLUSTERS
Two basic instrument cluster options are offered on
XJ (Cherokee) models. One is referred to as a low-
line cluster, and the other is referred to as a high-
line cluster. Each cluster is divided into two areas:
the gauge area, and the tell-tale area. Each area is
served by a separate printed circuit and wiring con-
nector. Some variations of each cluster exist due to
optional equipment and regulatory requirements.
The low-line cluster includes the following gauges:
²fuel gauge
²speedometer/odometer.
The low-line cluster includes provisions for the fol-
lowing indicator lamps:
²anti-lock brake system lamp
²brake warning lamp
²coolant temperature warning lamp
²four-wheel drive indicator lamps
²generator warning lamp
²headlamp high beam indicator lamp
²low oil pressure warning lamp
²low washer fluid warning lamp
²malfunction indicator (Check Engine) lamp
²seat belt reminder lamp
²turn signal indicator lamps
²upshift indicator lamp.
JINSTRUMENT PANEL AND GAUGES 8E - 1

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