1994 JEEP CHEROKEE cooling

plugs with scavenger deposits can be considered nor-
mal in condition and can be cleaned using standard
procedures.
CHIPPED ELECTRODE INSULATOR
A chipped electrode insulator usually results from
bending the center electrode while adjusting the
spark plug electrode gap. Under certain conditions,
severe detonation can also separate the insulator
from the center electrode (Fig. 27). Spark plugs with
this condition must be replaced.
PREIGNITION DAMAGE
Preignition damage is usually caused by excessive
combustion chamber temperature. The center elec-
trode dissolves first and the ground electrode dis-
solves somewhat latter (Fig. 28). Insulators appear
relatively deposit free. Determine if the spark plug
has the correct heat range rating for the engine. De-
termine if ignition timing is over advanced, or if
other operating conditions are causing engine over-
heating. (The heat range rating refers to the operat-
ing temperature of a particular type spark plug.
Spark plugs are designed to operate within specifictemperature ranges. This depends upon the thickness
and length of the center electrodes porcelain insula-
tor.)
SPARK PLUG OVERHEATING
Overheating is indicated by a white or gray center
electrode insulator that also appears blistered (Fig.
29). The increase in electrode gap will be consider-
ably in excess of 0.001 inch per 1000 miles of opera-
tion. This suggests that a plug with a cooler heat
range rating should be used. Over advanced ignition
timing, detonation and cooling system malfunctions
can also cause spark plug overheating.
SPARK PLUG SECONDARY CABLES
TESTING
Spark plug cables are sometimes referred to as sec-
ondary ignition cables or secondary wires. The cables
transfer electrical current from the distributor to in-
dividual spark plugs at each cylinder. The spark plug
cables are of nonmetallic construction and have a
built in resistance. The cables provide suppression of
radio frequency emissions from the ignition system.
Fig. 26 Scavenger Deposits
Fig. 27 Chipped Electrode Insulator
Fig. 28 Preignition Damage
Fig. 29 Spark Plug Overheating
JIGNITION SYSTEMS 8D - 17

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 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.
CAUTION: On some models, two bolts used to se-
cure 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
ENGINE AND AUTOMATIC TRANSMISSION
(1) Be sure the paper/cardboard spacer (Fig. 7) has
been installed to the bottom of the new sensor.If original sensor is being reinstalled (such as with
transmission or flywheel removal), clean bottom of
the sensor before installation. Obtain a new spacer
and remove the paper backing. Install the self-adhe-
sive side to bottom of sensor. This spacerMUSTbe
installed. If spacer is not installed, sensor will be
damaged when engine is started.
(2) Position sensor to transmission bellhousing and
install mounting bolt finger tight.
(3) Gently seat (push down) the sensor until the
paper spacer contacts the outer edge of the flywheel.
(4) Tighten sensor mounting bolt (Fig. 7) to 17-
to-21 Nzm (13-to-16 ft. lbs.) torque.
(5) Connect the electrical connector to sensor.
(6) Install the clip to sensor wire harness.
(7) Install clip over fuel rail mounting stud. Install
clip mounting nut.
ENGINE COOLANT TEMPERATURE SENSOR
WARNING: HOT, PRESSURIZED COOLANT CAN
CAUSE INJURY BY SCALDING. COOLING SYSTEM
MUST BE PARTIALLY DRAINED BEFORE REMOV-
ING THE COOLANT TEMPERATURE SENSOR. RE-
FER TO GROUP 7, COOLING.
REMOVAL
The sensor is installed in the thermostat housing
(Fig. 8).
(1) Drain cooling system until the coolant level is
below the cylinder head. For cooling system draining,
refer to Group 7, Cooling.
(2) Disconnect the coolant temperature sensor wire
connector.
(3) Remove the sensor from the thermostat hous-
ing (Fig. 8).
Fig. 7 Crankshaft Position SensorÐ4.0L EngineÐYJ
models With Automatic Transmission
Fig. 8 Coolant Temperature SensorÐTypical
8D - 22 IGNITION SYSTEMSJ

INSTALLATION
(1) Install coolant temperature sensor into the
thermostat housing. Tighten to 28 Nzm (21 ft. lbs.)
torque.
(2) Connect the wire connector.
(3) Fill the cooling system. Refer to group 7, Cool-
ing System.
DISTRIBUTOR
All distributors contain an internal oil seal that
prevents oil from entering the distributor housing.
The seal is not serviceable.
The camshaft position sensor is located in the dis-
tributor on all engines (Fig. 9).
Refer to Fig. 9 for an exploded view of the distrib-
utor.
REMOVALÐ2.5L 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.
(4) Disconnect the distributor wiring harness from
the main engine harness.
(5) Scribe a mark on the distributor housing in
line with the tip of the rotor. Note the position of the
rotor and distributor housing. This is in relation tothe surrounding engine components as reference
points for installing the distributor.
(6) Remove the distributor holddown bolt and
clamp.
(7) Remove the distributor from engine by lifting
straight up. Remove and discard old distributor-to-
engine block gasket. Note that the rotor will rotate
slightly in a counterclockwise direction while lifting
up the distributor. Note this position after removal.
INSTALLATIONÐ2.5L ENGINE
ENGINE NOT ROTATED AFTER REMOVAL
This procedure assumes that the engine was not ro-
tated with distributor out of engine.
(1) Clean the distributor mounting hole area of the
engine block.
(2) Install a new distributor-to-engine block gas-
ket.
There is a fork on the distributor housing where
the housing seats against the engine block. The slot
in the fork aligns with the distributor holddown bolt
hole in the engine block. The distributor is correctly
installed when the rotor is correctly positioned. This
is with the slot in the fork aligned with the hold-
down bolt hole in the cylinder block. Because of the
fork on the distributor housing, initial ignition tim-
ing is not adjustable (the distributor cannot be rotat-
ed).
(3) Position the distributor shaft in the cylinder
block. If the engine was not rotated while the distrib-
utor was removed, perform the following:
²Align the rotor tip with the scribe mark on the
distributor housing during removal. Turn the rotor
approximately 1/8-turn counterclockwise past the
scribe mark.
CAUTION: Be sure that the distributor shaft fully
engages into the oil pump drive gear shaft. It may
be necessary to slightly rotate (bump) the engine.
This is done while applying downward hand force
on the distributor body. It should fully engage the
distributor shaft with the oil pump drive gear shaft.
²Slide the distributor shaft down into the engine.
It may be necessary to move the rotor and shaft
(slightly) to engage the distributor shaft with the slot
in the oil pump shaft. The same may have to be done
to engage the distributor gear with the camshaft
gear. However, the rotor should align with the scribe
mark when the distributor shaft is down in place.
²Install the distributor holddown clamp and bolt.
Tighten the bolt to 23 Nzm (17 ft. lbs.) torque.
(4) Install the distributor cap (with the ignition ca-
bles) on the distributor housing (Fig. 10). Tighten
distributor cap holddown screws to 3 Nzm (26 in. lbs.)
torque.
(5) Connect the distributor wiring harness to the
main engine harness.
Fig. 9 DistributorÐ2.5L/4.0L EnginesÐTypical
JIGNITION SYSTEMS 8D - 23

The camshaft position sensor is located in the dis-
tributor on all engines (Fig. 9).
Refer to figure 9 for an exploded view of the dis-
tributor.
(1) Disconnect the negative battery cable at bat-
tery.
(2) On XJ models equipped with A/C, remove the
electrical cooling fan and shroud assembly from the
radiator. This will provide room to turn the engine
with a socket and ratchet using the vibration damper
bolt.
(3) Scribe a mark on the distributor housing. Do
this below the left side of (past) the number one
spark plug cable post of the distributor cap. This will
be used as a reference for #1 cylinder firing position
(Fig. 14).
(4) Remove the distributor cap from distributor (2
screws).
(5) Turn the engine in a clockwise direction until
the rotor is approaching the scribe mark on the dis-
tributor housing. Then slowly turn the engine until
the timing mark on the crankshaft vibration damper
lines up with zero on the front cover timing scale
(Fig. 15).
The timing mark is on the edge of the vibra-
tion damper closest to the engine front cover.
(6) Align the trailing edge of the rotor blade with
the scribe mark on the distributor housing (Fig. 16).
(7) Remove the distributor holddown bolt and
clamp.
(8) Remove the distributor from the engine by lift-
ing straight up. Remove and discard old distributor-
to-engine block gasket. Note that the rotor willrotate slightly in a counterclockwise direction while
lifting up the distributor. Note this position after re-
moval.
INSTALLATIONÐ4.0L ENGINE
(1) Clean the distributor mounting area of the cyl-
inder block.
(2) Install a replacement distributor-to-engine
block gasket.
(3) Using a flat blade screwdriver, turn the oil
pump gear shaft. Do this until the slot is slightly
past the 11 o'clock position (Fig. 17).
Fig. 13 Distributor Rotor PositionÐ2.5L EngineFig. 14 Mark Distributor Housing
Fig. 15 Align Timing Marks
JIGNITION SYSTEMS 8D - 25

The oil pump shaft is located down in the distribu-
tor hole.
(4) Install the rotor.
(5) Without engaging the distributor gear into the
cam gear, position the distributor into the hole in the
engine block. Be sure the distributor gasket is in-
stalled.
(6) Visually line up the holddown ear of the dis-
tributor housing with the holddown clamp hole (Fig.
18).
(7) Turn the rotor to the 4 o'clock position (Fig.
19).
(8) Slide the distributor down into the block until
it seats. Keep the holddown ear aligned to the hole
in the block.
(9) The rotor should be in the 5 o'clock position.
This is with the trailing edge of rotor blade lined up
with scribe mark on distributor housing (number one
spark plug cable post location).(10) Install the distributor holddown clamp bolt
and tighten to 23 Nzm (17 ft. lbs.) torque.
(11) Install the distributor cap and connect the dis-
tributor electrical connector.
(12) Install electrical cooling fan and shroud if ap-
plicable.
(13) 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.
Fig. 16 Align Rotor Trailing Edge With Scribe Mark
Fig. 17 Align Oil Pump Gear ShaftÐ4.0L Engine
Fig. 18 Distributor InstallationÐTypical
Fig. 19 Rotor Alignment
8D - 26 IGNITION SYSTEMSJ

WIRING DIAGRAMS XJ
INDEX
Wiring Diagram Name Sheet Number
A/C Compressor Clutch Relay...................3,69
A/C Compressor Clutch........................69
A/C Heater Blower Motor.......................70
A/C Low Pressure Switch.......................69
A/C Mode Select Switch........................70
A/C Thermostat..............................69
ABS Diode.................................33
ABS Green Indicator Lamp......................57
ABS Hydraulic Actuation Unit.....................33
ABS #1 Relay.............................3,31
ABS #2 Relay.............................3,31
ABS Pump Motor............................30
ABS Red Indicator Lamp.......................57
Ambient Temperature Sensor.....................53
Antenna...................................71
Antenna Mast...............................71
Anti-Lock Brake Control Module Connector...........109
Anti-Lock Braking System...............29,30,31,32,33
ABS Diode...............................33
ABS Relays...............................31
Anti-Lock Pump Motor.......................30
Anti-Lock Brake System Module.........29,30,31,32,33
Data Link Connector.........................32
G Sensor................................30
Hydraulic Actuation Unit......................33
Left Front Wheel Sensor......................29
Left Rear Wheel Sensor.......................29
Pedal Travel Sensor.........................30
Right Front Wheel Sensor.....................29
Right Rear Wheel Sensor......................29
Anti-Lock Brake System Module...........29,30,31,32,33
Anti-Lock Pump Motor.........................30
Anti-Lock Relay..............................31
Ashtray Lamp...............................48
Automatic Shut Down Relay..................3,12,17
Automatic Transmission Control System (2.5L).........27
Front Axle Lock-Up Switch.....................27
EMCC Relay..............................27
EMCC Solenoid............................27
Back-Up Lamp Switch.........................25
Ballast Resistor..............................89
Battery..................................1,7,8
Blower Motor.............................68,70
Blower Resistors...........................68,70
Blower Switch............................68,70
Body Ground...............................44
Brake Warning Switch.........................67
Bulkhead Disconnect.................101,102,103,104
Camshaft Position Sensor.....................11,20
Cargo Lamp................................50
Center High Mounted Stop Lamp..................98
Charging System 2.5L..........................5
Generator.................................5Wiring Diagram Name Sheet Number
Charging System 4.OL..........................6
Generator.................................6
Chime Module..............................74
Ignition Key Warning Switch....................74
Seat Belt Switch...........................74
Cigar Lighter...............................37
Cigar Lighter Lamp...........................48
Circuit Breakers
In Line Circuit Breaker........................2
Trailer Tow In-Line Circuit Breaker................97
Windshield Wiper Circuit Breaker...............63,64
Connectors
Anti-Lock Brake Control Module Connector.........109
Data Link Connector...................16,18,25,32
Instrument Cluster Connector................55,108
Main Body Connectors.......................112
Power Mirror Connector......................110
Powertrain Control Module Connector.............111
Remote Keyless Entry Module Connector...........114
Steering Column Connector...................106
Telltale Connector........................56,107
Trailer Tow Connector........................93
Transmission Control Module Connector...........105
Cooling Fan Relay...........................3,23
Courtesy Lamp..............................49
Crankshaft Position Sensor....................11,20
Data Link Connector....................16,18,25,32
Daytime Running Lamp Module (DRL)...............38
Daytime Running Lamp System...................38
Diode,ABS.................................33
Distributor Ignition Coil.......................16,18
Dome Lamp................................51
Dome And Courtesy Lamps..................49,50,51
Cargo Lamp..............................50
Dome Lamp..............................51
Dome/Reading Lamp.........................51
Glove Box Lamp...........................49
Left Courtesy Lamp.........................49
Reading Lamp.............................51
Right Courtesy Lamp........................49
Vanity Lamps.............................51
Dome Reading Lamp..........................51
Door Jamb Switch System....................75,76
Left Front Door Jamb Switch...................75
Left Rear Door Jamb Switch...................75
Liftgate Switch............................76
Right Front Door Jamb Switch..................76
Right Rear Door Jamb Switch..................76
EMCC Relay...............................3,27
EMCC Solenoid..............................27
Engine Block Coolant Heater/Cigar Lighter............37
Cigar Lighter..............................37
Engine Block Coolant Heater....................37
JWIRING DIAGRAMS 8W - 149

Wiring Diagram Name Sheet Number
Fuse #15...............................1,41
Fuse #17...........................2,10,55,74
Fuse #18...............................1,66
Fuse #19.............................1,41,47
Gauges
Engine Coolant Temperature Gauge...........59,60,61
Engine Oil Pressure Gauge.................59,60,61
Fuel Gauge...........................59,60,61
G Sensor..................................30
Generator.................................5,6
Glove Box Lamp.............................49
Hazard Flasher............................35,46
Headlamp Delay Module........................43
Headlamp Dimmer Switch.......................41
Headlamp Switch...........................41,42
Fog Lamp Illumination........................42
Fog Lamp Switch...........................42
Headlamp Dimmer Switch.....................41
Headlamp Switch...........................41
Headlamps...............................39,40
Heat Mode Select Switch.......................68
Heated Oxygen Sensor.......................13,21
Heated Rear Window..........................66
Relay...................................66
Grid...................................66
Switch..................................66
Heated Rear Window Switch Lamp.................47
Heater A/C Panel Lamp........................47
Heater and A/C System......................69,70
A/C Mode Selector Switch.....................70
A/C Compressor Clutch.......................69
A/C Compressor Clutch Relay...................69
A/C Heater Blower Motor......................70
A/C Thermostat............................69
A/C Low Pressure Switch.....................69
Blower Resistor............................70
Blower Switch.............................70
Powertrain Control Module.....................69
Heat Mode Select Switch.......................68
Heater Blower Motor..........................68
Heater,Engine Block...........................37
Heater System..............................68
Blower Resistor............................68
Blower Switch.............................68
Heater Blower Motor.........................68
Heater Mode Select Switch....................68
Heavy Duty Cooling 4.OL.......................23
Fan Control Relay...........................23
Powertrain Control Module.....................23
Radiator Fan Motor.........................23
High Beam Indicator Lamp..................59,60,61
High Beam Relay............................40
Hi-Line Instrument Cluster.......................61
Horn Brush/Slip Ring..........................34
Horn Relay................................34
Horn Switch................................34
Horns....................................34
Hydraulic Actuation Unit, ABS....................33Wiring Diagram Name Sheet Number
Idle Air Control Motor.......................15,22
Ignition Key Warning Switch.....................74
Ignition Switch..............................2,9
Ignition System............................9,10
Injectors................................15,22
In Line Circuit Breaker..........................2
Instrument Cluster............................55
Powertrain Control Module.....................55
Washer Fluid Level Switch.....................55
Instrument Cluster (Hi-Line)......................61
Instrument Cluster (Lo-Line).....................60
Instrument Cluster (Standard)....................59
Instrument Cluster Connector..................55,108
Instrument Cluster Printed Circuit Board (W/ABS).......57
Instrument Cluster Printed Circuit Board (W/O ABS)......58
Instrument Cluster Indicators.....................56
Instrument Panel Ground.......................62
Instrument Panel Illumination...................47,48
Ashtray Lamp.............................48
Cigar Lighter Lamp..........................48
Fog Lamp Illumination........................47
Heater A/C Panel Lamp.......................47
Heater Rear Window Switch Lamp................47
Rear Wiper Wash Switch Lamp..................47
Transfer Case Lamp.........................48
Transmission Range Switch Lamp................48
Intake Air Temperature Sensor..................14,19
Intermittent Front Wipers/Washers.................64
Intermittent Wiper Module.......................64
Lamps
ABS Green Indicator Lamp.....................57
ABS Red Indicator Lamp......................57
Ashtray Lamp.............................48
Cargo Lamp..............................50
Center High Mounted Stop Lamps................98
Cigar Lighter Lamp..........................48
Dome Lamp..............................51
Dome/Reading Lamp.........................51
Fog Lamp Illumination........................47
4WD Indicator Lamp.....................26,57,58
Full Time Indicator Lamp....................57,58
Glove Box Lamp...........................49
Heated Rear Window Switch Lamp...............47
Heater A/C Panel Lamp.......................47
High Beam Indicator Lamp.................59,60,61
Indicator Lamp 4WD.......................57,58
Instrument Cluster Illumination Lamps.........59,60,61
Left Back-Up Lamp........................91,93
Left Courtesy Lamp.........................49
Left Fog Lamp.............................39
Left Headlamp.............................39
Left Park/Turn Signal Lamp....................39
Left Side Marker Lamp (Front)..................39
Left Side Marker Lamp (Rear)................91,93
Left Tail/Stop Lamp.......................91,93
Left Turn Indicator Lamp..................59,60,61
Left Turn Lamp (Amber)....................91,93
Left Vanity Lamp...........................51
JWIRING DIAGRAMS 8W - 151

Wiring Diagram Name Sheet Number
Right Power Mirror.........................73
Power Mirrors.............................73
Power Seat..............................77,78
Left Power Seat Motor Assembly................77
Left Power Seat Switch.......................78
Power Steering Pressure Switch...................15
Powertrain Control Module......11,12,13,14,15,16,17,18,19,
20,21,22,23,35,36,45,55,69
Powertrain Control Module (PCM) Connector..........111
Power Windows.......................79,80,81,82
Left Front Door Window Motor..................81
Left Rear Door Window Motor..................82
Left Rear Door Window Switch..................82
Power Window Switch.......................79
Right Front Door Window Switch................81
Right Front Door Window Motor.................81
Right Rear Door Window Motor.................82
Right Rear Door Window Switch.................82
Power Window Switch.........................79
Printed Circuit Boards.................57,58,59,60,61
Pumps
Front Washer...........................63,64
Rear Washer..............................65
Radiator Fan Motor...........................23
Radio....................................71
Antenna Mast.............................71
Left Front Door Speaker......................71
Left Instrument Panel Speaker..................71
Left Liftgate Speaker.........................72
Right Front Door Speaker.....................72
Right Instrument Panel Speaker.................72
Right Liftgate Speaker........................72
Reading Lamps..............................51
Rear Lighting...................91,92,93,94,95,96,97
Left Back-Up Lamp........................91,93
Left Side Marker Lamp (Rear)................91,93
Left Tail/Stop Lamp.......................91,93
Left Turn Lamp (Amber)....................91,93
Left Turn Relay............................97
License Lamp...........................91,95
Right Back-Up Lamp.......................92,96
Right Side Marker Lamp (Rear)...............92,96
Right Tail/Stop Lamp......................92,96
Right Turn Lamp (Amber)...................92,96
Right Turn Relay...........................97
Stop Lamp Relay...........................97
Trailer Tow Connector........................93
Trailer Tow In-Line Circuit Breaker................97
Rear Lighting With Trailer Tow............93,94,95,96,97
Rear Lighting Without Trailer Tow................91,92
Rear Washer Pump...........................65
Rear Wiper Motor............................65
Rear Wiper/Washer Motor.......................65
Rear Washer Pump...........................65
Rear Wiper Motor............................65
Rear Wiper/Washer Switch......................65
Rear Wiper/Washer Switch Lamp..................47
Reed Switch................................26Wiring Diagram Name Sheet Number
Relays
ABS #1 Relay............................3,31
ABS #2 Relay............................3,31
A/C Compressor Clutch Relay..................3,69
Automatic Shut Down Relay.................3,12,17
Cooling Fan Relay...........................3
EMCC Relay.............................3,27
Engine Starter Relay.......................3,7,8
Fan Control Relay...........................23
Fuel Pump Relay........................3,12,17
Heated Rear Window Relay....................66
High Beam Relay...........................40
Horn Relay...............................34
L.C.D. Illumination Relay......................52
Left Turn Relay............................97
Park Lamp Relay...........................39
Power Door Lock Relay.......................83
Power Door Unlock Relay.....................83
Right Turn Relay...........................97
Stop Lamp Relay...........................97
Relay Center Identification......................113
Remote Keyless Entry System....................28
Remote Keyless Entry Module...................28
Remote Keyless Entry Module Connector...........114
Resistor,Ballast..............................39
Resistor,Blower..............................68
Right Front Door Jamb Switch....................76
Right Front Door Speaker.......................72
Right Front Door Window Switch..................81
Right Front Wheel Sensor.......................29
Right Front Door Connector and Door Lock Switch
Function Chart.............................87
Right Front Door Lock Motor.....................86
Right Instrument Panel Speaker...................72
Right Liftgate Speaker.........................72
Right Front Door Window Connector and Window Lift
Switch Function Chart........................87
Right Rear Door Jamb Switch....................76
Right Rear Door Window Connector and Window Lift
Function Chart.............................88
Right Rear Wheel Sensor.......................29
Right Turn Relay.............................97
Seat Belt Switch.............................74
Seat Belt Warning Indicator Lamp................57,58
Sensors
Ambient Temperature Sensor...................53
Camshaft Position Sensor...................11,20
Crankshaft Position Sensor...................11,20
Engine Coolant Temperature Sensor.............14,19
G Sensor................................30
Heated Oxygen Sensor.....................13,21
Intake Air Temperature Sensor................14,19
Left Front Wheel Sensor......................29
Left Rear Wheel Sensor.......................29
MAP Sensor............................14,19
Pedal Travel Sensor.........................30
Right Front Wheel Sensor.....................29
Right Rear Wheel Sensor......................29
JWIRING DIAGRAMS 8W - 153