1995 JEEP CHEROKEE wiring

DIAGNOSIS
COMPASS/DISPLAY SELF-DIAGNOSTIC TEST
This self-diagnostic test is used to determine that
the compass and all of its display segments are oper-
ating properly electrically. Initiate the self-diagnostic
test as follows:
(1) With the ignition switch in the OFF position,
simultaneously press and hold the COMP/TEMP but-
ton and the US/METRIC button.
(2) Turn ignition switch to the ON position.
(3) Continue to hold both buttons until the display
performs a walking segment test. In this test all of
the compass points are displayed, along with various
number combinations. These combinations verify that
all display segments are functional. If any segment
should fail to light during the test, the unit is faulty
and requires replacement. To repeat the test, momen-
tarily depress and release the COMP/TEMP button
one time.
(4) Momentarily depress and release the US/MET-
RIC button one time and all segments will light si-
multaneously for about 2 seconds. If any segment
should fail to light during the test, the unit is faulty
and requires replacement. To repeat the test, momen-
tarily depress and release the COMP/TEMP button
one time.
(5) Momentarily depress and release the US/MET-
RIC button one time or turn the ignition switch to
OFF to exit the self-diagnostic mode and return to
normal operation.
If the compass functions, but accuracy is sus-
pect, it may be necessary to perform a variation
adjustment. This procedure allows the unit to
accommodate variations in the earth's mag-
netic field strength based on geographic loca-
tion. See Compass Variation Adjustment, in this
group.
If the compass display has blanked out and
only CAL appears, demagnetizing may be nec-
essary to remove excessive residual magnetic
fields from the vehicle. See Compass Demagne-
tizing, in this group.
THERMOMETER DIAGNOSIS
The thermometer function is supported by a tem-
perature sensor, a wiring circuit and a portion of the
overhead console display. The sensor is mounted at
the center of the vehicle below the grille, behind the
front bumper (Fig. 1).
If any portion of the circuit fails, it will self-diag-
nose as an open or short circuit. The system will dis-
play SC (short circuit) when the sensor is exposed to
temperatures in excess of 55ÉC (131ÉF) or if the cir-
cuit is shorted. If the temperature is below -40ÉC
(-40ÉF) or an open circuit exists, the system will dis-
play OC (open circuit).To diagnose the temperature sensor, perform the
following procedures. If the sensor and circuit are
OK, then the electronic module is faulty and should
be replaced.
SENSOR TEST
(1) Turn the ignition switch to OFF. Unplug sensor
connector.
(2) Measure resistance of sensor. At -40ÉF the re-
sistance is 336K ohms. At 140ÉF the resistance is
2.488K ohms. Sensor resistance should read between
these two values. If OK, go to Sensor Circuit Test. If
not OK, replace the sensor.
SENSOR CIRCUIT TEST
(1) Turn ignition switch to OFF. Unplug sensor
connector.
(2) Short the pins on the body half of connector us-
ing a jumper wire.
(3) Remove the overhead console as described in
Service Procedures.
(4) Check continuity between cavities 10 and 11 of
overhead console harness connector (Fig. 2). There
should be continuity. If OK, go to next step. If not
OK, repair open circuit as required.
Fig. 1 Temperature Sensor
8C - 2 OVERHEAD CONSOLEJ

DIAGNOSTICS/SERVICE PROCEDURES
INDEX
page page
Automatic Shutdown (ASD) Relay Test.......... 6
Camshaft Position Sensor Test................ 6
Crankshaft Position Sensor Test............... 7
Distributor Cap............................ 7
Distributor Rotor........................... 8
DRB Scan Tool............................ 8
Engine Coolant Temperature Sensor Test........ 9
General Information........................ 6
Ignition Coil.............................. 9
Ignition Secondary Circuit Diagnosis........... 10Ignition Timing............................ 11
Intake Manifold Air Temperature Sensor Test..... 11
Manifold Absolute Pressure (MAP) Sensor Test . . . 11
On-Board Diagnostics...................... 15
Oxygen (O2S) Sensor Tests................. 15
Powertrain Control Module (PCM)............. 11
Spark Plug Secondary Cables................ 14
Spark Plugs............................. 12
Throttle Position Sensor Test................. 15
GENERAL INFORMATION
This section of the group, Diagnostics/Service Pro-
cedures, will discuss basic ignition system diagnostics
and service adjustments.
For system operation and component identification,
refer to the Component Identification/System Opera-
tion section of this group.
For removal or installation of ignition system com-
ponents, refer to the Component Removal/Installa-
tion section of this group.
For other useful information, refer to the On-Board
Diagnostics section.
For operation of the DRB Scan Tool, refer to the
appropriate Powertrain Diagnostic Procedures ser-
vice manual.
AUTOMATIC SHUTDOWN (ASD) RELAY TEST
To perform a complete test of this relay and its cir-
cuitry, refer to the DRB scan tool. Also refer to the
appropriate Powertrain Diagnostics Procedures man-
ual. To test the relay only, refer to RelaysÐOpera-
tion/Testing in the Group 14, Fuel Systems section.
CAMSHAFT POSITION SENSOR TEST
To perform a complete test of this sensor and its
circuitry, refer to the DRB scan tool. Also refer to the
appropriate Powertrain Diagnostics Procedures man-
ual. To test the sensor only, refer to the following:
The camshaft position sensor is located in the dis-
tributor (Fig. 1).
To perform a complete test of this sensor and its
circuitry, refer to the DRB scan tool. Also refer to the
appropriate Powertrain Diagnostics Procedures man-
ual. To test the sensor only, refer to the following:
For this test, an analog (non-digital) voltme-
ter is needed.Do not remove the distributor connec-
tor from the distributor. Using small paper clips,
insert them into the backside of the distributor wire
harness connector to make contact with the termi-nals. Be sure that the connector is not damaged
when inserting the paper clips. Attach voltmeter
leads to these paper clips.
(1) Connect the positive (+) voltmeter lead into the
sensor output wire. This is at done the distributor
wire harness connector. For wire identification, refer
to Group 8W, Wiring Diagrams.
(2) Connect the negative (-) voltmeter lead into the
ground wire. For wire identification, refer to Group
8W, Wiring Diagrams.
(3) Set the voltmeter to the 15 Volt DC scale.
(4) Remove distributor cap from distributor (two
screws). Rotate (crank) the engine until the distribu-
tor rotor is pointed to approximately the 11 o'clock
position. The movable pulse ring should now be
within the sensor pickup.
(5) Turn ignition key to ON position. The voltmeter
should read approximately 5.0 volts.
(6) If voltage is not present, check the voltmeter
leads for a good connection.
(7) If voltage is still not present, check for voltage
at the supply wire. For wire identification, refer to
Group 8W, Wiring Diagrams.
Fig. 1 Camshaft Position SensorÐTypical
8D - 6 IGNITION SYSTEMSJ

IGNITION SECONDARY CIRCUIT DIAGNOSIS
CHECKING FOR SPARK
CAUTION: When disconnecting a high voltage cable
from a spark plug or from the distributor cap, twist
the rubber boot slightly (1/2 turn) to break it loose
(Fig. 12). Grasp the boot (not the cable) and pull it
off with a steady, even force.
(1) Disconnect the ignition coil secondary cable
from center tower of the distributor cap. Hold the ca-
ble terminal approximately 12 mm (1/2 in.) from a
good engine ground (Fig. 13).
WARNING: BE VERY CAREFUL WHEN THE ENGINE
IS CRANKING. DO NOT PUT YOUR HANDS NEAR
THE PULLEYS, BELTS OR THE FAN. DO NOT WEAR
LOOSE FITTING CLOTHING.
(2) Rotate (crank) the engine with the starter mo-
tor and observe the cable terminal for a steady arc. If
steady arcing does not occur, inspect the secondary
coil cable. Refer to Spark Plug Cables in this group.
Also inspect the distributor cap and rotor for cracksor burn marks. Repair as necessary. If steady arcing
occurs, connect ignition coil cable to the distributor
cap.
(3) Remove a cable from one spark plug.
(4) Using insulated pliers, hold the cable terminal
approximately 12 mm (1/2 in.) from the engine cylin-
der head or block while rotating the engine with the
starter motor. Observe the spark plug cable terminal
for an arc. If steady arcing occurs, it can be expected
that the ignition secondary system is operating cor-
rectly.(note that if the ignition coil cable is re-
moved for this test, instead of a spark plug
cable, the spark intensity will be much higher.)
If steady arcing occurs at the spark plug cables, but
the engine will not start, connect the DRB scan tool.
Refer to the Powertrain Diagnostic Procedures ser-
vice manual.
FAILURE TO START TEST
To prevent unnecessary diagnostic time and wrong
test results, the previous Checking For Spark test
should be performed prior to this test.
WARNING: SET PARKING BRAKE OR BLOCK THE
DRIVE WHEELS BEFORE PROCEEDING WITH THIS
TEST.
(1) Unplug the ignition coil harness connector at
the coil (Fig. 14).
(2) Connect a set of small jumper wires (18 gauge
or smaller) between the disconnected harness termi-
nals and the ignition coil terminals. To determine po-
larity at connector and coil, refer to the Wiring
Diagrams section.
(3) Attach one lead of a voltmeter to the positive
(12 volt) jumper wire. Attach the negative side of
voltmeter to a good ground. Determine that sufficient
battery voltage (12.4 volts) is present for the starting
and ignition systems.
Fig. 12 Cable Removal
Fig. 13 Checking for SparkÐTypical
Fig. 14 Coil Harness ConnectorÐTypical (4.0L
Shown)
8D - 10 IGNITION SYSTEMSJ

(4) Crank the engine for 5 seconds while monitor-
ing the voltage at the coil positive terminal:
²If the voltage remains near zero during the entire
period of cranking, refer to On-Board Diagnostics in
Group 14, Fuel Systems. Check the powertrain con-
trol module (PCM) and auto shutdown relay.
²If voltage is at or near battery voltage and drops
to zero after 1-2 seconds of cranking, check the cam-
shaft position sensor-to-PCM circuit. Refer to On-
Board Diagnostics in Group 14, Fuel Systems.
²If voltage remains at or near battery voltage dur-
ing the entire 5 seconds, turn the key off. Remove
the 60-way connector (Fig. 15) from the PCM. Check
60-way connector for any spread terminals.
(5) Remove test lead from the coil positive termi-
nal. Connect an 18 gauge jumper wire between the
battery positive terminal and the coil positive termi-
nal.
(6) Make the special jumper shown in figure 16.
Using the jumper,momentarilyground pin/cavity
number 19 of the PCM 60-way connector. A spark
should be generated at the coil cable when the
ground is removed.
(7) If spark is generated, replace the powertrain
control module (PCM).
(8) If spark is not seen, use the special jumper to
ground the coil negative terminal directly.
(9) If spark is produced, repair wiring harness for
an open condition.
(10) If spark is not produced, replace the ignition
coil.IGNITION TIMING
Base (initial) ignition timing is NOT adjust-
able on any of the 2.5L 4-cylinder or 4.0L 6-cyl-
inder engines. Do not attempt to adjust ignition
timing by rotating the distributor.
Do not attempt to modify the distributor
housing to get distributor rotation. Distributor
position will have no effect on ignition timing.
All ignition timing functions are controlled by the
powertrain control module (PCM). Refer to On-Board
Diagnostics in the Multi-Port Fuel InjectionÐGen-
eral Diagnosis section of Group 14, Fuel Systems for
more information. Also refer to the appropriate Pow-
ertrain Diagnostics Procedures service manual for op-
eration of the DRB Scan Tool.
INTAKE MANIFOLD AIR TEMPERATURE SENSOR
TEST
For an operational description, diagnosis or remov-
al/ installation procedures, refer to Group 14, Fuel
Systems.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
TEST
For an operational description, diagnosis and re-
moval/installation procedures, refer to Group 14,
Fuel System.
POWERTRAIN CONTROL MODULE (PCM)
The PCM (formerly referred to as the SBEC or en-
gine controller) is located in the engine compartment
behind the windshield washer fluid tank on YJ mod-
els (Fig. 17). It is located in the engine compartment
next to the air cleaner on XJ models (Fig. 18).
The ignition system is controlled by the PCM.
For removal and installation of this component, re-
fer to the Component Removal/Installation section of
this group.
Fig. 15 PCM 60-Way Connector
Fig. 16 Special Jumper Ground-to-Coil Negative
Terminal
Fig. 17 PCM LocationÐYJ Models
JIGNITION SYSTEMS 8D - 11

COMPONENT REMOVAL/INSTALLATION
INDEX
page page
Automatic Shutdown (ASD) Relay............. 17
Camshaft Position Sensor................... 17
Crankshaft Position Sensor.................. 17
Distributor............................... 19
Engine Coolant Temperature Sensor........... 19
General Information....................... 17
Ignition Coil............................. 22Intake Manifold Air Temperature Sensor......... 23
Manifold Absolute Pressure (MAP) Sensor....... 23
Oxygen (O2S) Sensor...................... 23
Powertrain Control Module (PCM)............. 23
Spark Plug Secondary Cables................ 24
Spark Plugs............................. 23
Throttle Position Sensor (TPS)............... 25
GENERAL INFORMATION
This section of the group, Component Removal/In-
stallation, will discuss the removal and installation
of ignition system components.
For basic ignition system diagnostics and service
adjustments, refer to the Diagnostics/Service Proce-
dures section of this group.
For system operation and component identification,
refer to the Component Identification/System Opera-
tion section of this group.
AUTOMATIC SHUTDOWN (ASD) RELAY
The ASD relay is installed in the power distribu-
tion center (PDC) (Figs. 1 or 2). Relay location is
printed on the PDC cover.
REMOVAL
(1) Remove the PDC cover.
(2) Remove the relay by lifting straight up.
INSTALLATION
(1) Check the condition of relay wire terminals at
PDC before installing relay. Repair as necessary.
(2) Push the relay into the connector.
(3) Install the relay cover.
CAMSHAFT POSITION SENSOR
The camshaft position sensor is located in the dis-
tributor (Fig. 3).
REMOVAL
Distributor removal is not necessary to remove
camshaft position sensor.
(1) Disconnect negative battery cable at battery.
(2) Remove distributor cap from distributor (two
screws).
(3) Disconnect camshaft position sensor wiring
harness from main engine wiring harness.
(4) Remove distributor rotor from distributor shaft.
(5) Lift the camshaft position sensor assembly
from the distributor housing (Fig. 3).
INSTALLATION
(1) Install camshaft position sensor to distributor.
Align sensor into notch on distributor housing.
(2) Connect wiring harness.
(3) Install rotor.
(4) Install distributor cap. Tighten mounting
screws.
CRANKSHAFT POSITION SENSOR
The crankshaft position sensor is mounted in the
Fig. 1 PDCÐXJ Models
Fig. 2 PDCÐYJ Models
JIGNITION SYSTEMS 8D - 17

REMOVALÐ2.5L OR 4.0L ENGINE
(1) Disconnect the negative battery cable at the
battery.
(2) Disconnect coil secondary cable at coil.
(3) Remove distributor cap from distributor (2
screws). Do not remove cables from cap. Do not re-
move rotor.
(4) Disconnect the distributor wiring harness from
the main engine harness.
(5) Remove the cylinder number 1 spark plug.
(6) Hold a finger over the open spark plug hole.
Rotate the engine at the vibration dampener bolt un-
til compression (pressure) is felt.
Slowly continue to rotate the engine. Do this until
the timing index mark on the vibration damper pul-
ley aligns with the top dead center (TDC) mark (0
degree) on timing degree scale (Fig. 9). Always rotate
the engine in direction of normal rotation. Do not ro-
tate the engine backward to align the timing marks.
On XJ models equipped with A/C, remove the elec-
trical cooling fan and shroud assembly from the radi-
ator. Refer to Group 7, Cooling System for
procedures.
This will provide room to turn the engine crank-
shaft with a socket and ratchet using the vibration
damper bolt.
(7) Remove the distributor holddown bolt and
clamp (Fig. 8).
(8) Remove the distributor from engine by slowly
lifting straight up.
Note that the rotor will rotate slightly in a counter-
clockwise direction while lifting up the distributor.
The oil pump gear will also rotate slightly in a coun-terclockwise direction while lifting up the distributor.
This is due to the helical cut gears on the distributor
and camshaft.
Note the removed position of the rotor during dis-
tributor removal. During installation, this will be re-
ferred to as the Pre-position.
2.5L 4-Cylinder Engine:Observe the slot in the
oil pump gear through the hole on the side of the en-
gine. It should be slightly before (counterclockwise of)
the 10 o'clock position (Fig. 10).
4.0L 6-Cylinder Engine:Observe the slot in the
oil pump gear through the hole on the side of the en-
gine. It should be slightly before (counterclockwise of)
the 11 o'clock position (Fig. 11).
(9) Remove and discard the old distributor-to-en-
gine block gasket (Fig. 8).
INSTALLATION
(1) If the engine crankshaft has been rotated after
distributor removal, cylinder number 1 must be re-
turned to its proper firing stroke. Refer to the previ-
ous REMOVAL steps number 5 and 6. These steps
must be done before installing distributor.
Fig. 9 Align Timing Marks
Fig. 10 Slot At 10 O'clock PositionÐ2.5L Engine
Fig. 11 Slot At 11 O'clock PositionÐ4.0L Engine
8D - 20 IGNITION SYSTEMSJ

²the number 1 cylinder piston is set at top dead
center (TDC) (compression stroke).
²the centerline of the slot at the base of the distrib-
utor is aligned to the centerline of the distributor
holddown bolt hole on the engine. In this position,
the holddown bolt should easily pass through the slot
and into the engine.
No adjustments are necessary. Proceed to next
step.(12) Install the distributor holddown clamp and
bolt. Tighten the bolt to 23 Nzm (17 ft. lbs.) torque.
(13) Remove the pin punch tool from the distribu-
tor. Or, if the plastic alignment pin was used, remove
it straight down from the bottom of the distributor.
Discard plastic pin.
(14) If removed, install the camshaft position sen-
sor to the distributor. Align the wiring harness grom-
met to the notch in the distributor housing.
(15) Install the rotor.
CAUTION: If the distributor cap is incorrectly posi-
tioned on distributor housing, the cap or rotor may
be damaged when engine is started.
(16) Install the distributor cap. Tighten distributor
cap holddown screws to 3 Nzm (26 in. lbs.) torque.
(17) If removed, install the spark plug cables to
the distributor cap. For proper firing order, refer to
the Specifications section at the end of this group.
See Engine Firing Order.
(18) Connect the distributor wiring harness to the
main engine harness.
(19) Connect battery cable to battery.
IGNITION COIL
The ignition coil is an epoxy filled type. If the coil
is replaced, it must be replaced with the same type.
REMOVAL
On the 2.5L 4-cylinder engine, the ignition coil is
mounted to a bracket on the side of the engine (to
the rear of the distributor).
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. 16).
(1) Disconnect the ignition coil secondary cable
from ignition coil (Fig. 16).
(2) Disconnect engine harness connector from igni-
tion coil.
Fig. 14 Distributor Engaged PositionÐ2.5L
4-Cylinder Engine
Fig. 15 Distributor Engaged PositionÐ4.0L
6-Cylinder Engine
Fig. 16 Ignition CoilÐTypical (4.0L Shown)
8D - 22 IGNITION SYSTEMSJ

IGNITION SWITCHÐXJ MODELS
IGNITION SWITCH AND KEY CYLINDER SERVICE
The ignition switch is located on the steering col-
umn. The Key-In-Switch and Halo Light are integral
with the ignition switch. Refer to Group 8U for Key-
In-Switch and Halo Light diagnosis for XJ models.
Refer to Group 8W, Wiring for ignition switch wir-
ing circuits.
REMOVAL
(1) Disconnect negative battery cable from battery.
(2) If vehicle has a tilt column, remove tilt lever by
turning it counterclockwise.
(3) Remove upper and lower covers from steering
column (Fig. 1).
(4) Remove ignition switch mounting screws. Use
tamper proof torx bit Snap-on TTXR20A2 or equiva-
lent to remove the screws (Fig. 2 or 3).
(5) Gently pull switch away from column. Release
connector locks on 7-terminal wiring connector, then
remove connector from ignition switch.
(6) Release connector lock on 4-terminal connector,
then remove connector from ignition switch (Fig. 4).
(7) To remove key cylinder from ignition switch:
(a) Insert key in ignition switch. Turn key to
LOCK position. Using a TTXR20A2 or equivalent
torx bit, remove key cylinder retaining screw and
bracket (Fig. 5 or 6).
(b) Rotate key clockwise to the OFF position.
Key cylinder will unseat from ignition switch (Fig.
7). When key cylinder is unseated, it will be ap-proximately 1/8 inch away from ignition switch
halo light ring.Do not attempt to remove key
cylinder at this time.
(c) With key cylinder in unseated position, rotate
key counterclockwise to the lock position and re-
move key.
(d) Remove key cylinder from ignition switch
(Fig. 8).
Fig. 1 Shroud Removal/InstallationÐTypical
Fig. 2 Ignition Switch Screw Removal
Fig. 3 Ignition Switch Screw Removal
8D - 26 IGNITION SYSTEMSJ