fuse JEEP CHEROKEE 1994 Service Repair Manual

scan tool will be necessary to determine which ABS
component has malfunctioned.
ABS Light Illuminates During Brake Stop
A system fault such as loss of speed sensor signal
or solenoid failure, will cause the amber warning
light to illuminate. The most effective procedure here
is to check for obvious damage first. Then check the
electronic components with the DRB II scan tool.
BRAKE WARNING LIGHT DISPLAY
The red brake warning light and the ABS light op-
erate independently. If the red light remains on after
startup or illuminates during a brake stop, refer to
the standard brake system diagnosis section. Either
the parking brakes are applied, or a wheel brake
malfunction has occurred.
ECU DIAGNOSIS
The ECU controls all phases of antilock system op-
eration. It also differentiates between normal and an-
tilock mode braking.
The ECU monitors and processes the signals gen-
erated from all of the system sensors at all times.
The ECU program includes a self check routine
that tests each of the system components. The self
check occurs during both phases of the initialization
program. A failure of the self check program will
cause the immediate illumination of the amber warn-
ing light. The light will also illuminate if a solenoid
or other system component fails during the dynamic
phase of initialization.
If a system malfunction should occur, do not imme-
diately replace the ECU. A blown system fuse, bad
chassis ground, or loss of feed voltage will each cause
a system malfunction similar to an ECU failure.
Never replace the ECU unless diagnosis with the
DRB II scan tool indicates this is necessary.
HCU DIAGNOSIS
The HCU pump and motor and solenoid valve body
are serviced only as an assembly. The HCU assembly
should not be replaced unless a fault has actually
been confirmed. Verify fault conditions with the DRB
II scan tool before proceeding with repair.
ABS SYSTEM WIRING AND ELECTRICAL CIRCUITS
Location of the ABS fuse (in the fuse panel) is
shown in Figure 1. The engine compartment harness
routing for the ABS components is shown in Figure 2.
ABS FAULT DIAGNOSIS
The fault diagnosis chart provides additional infor-
mation on potential ABS system faults. Use the
chart as a guide when diagnosing a system problem.
Fig. 1 ABS Fuse Location
5 - 4 BRAKESJ

SPECIFICATIONS
IGNITION OFF DRAW (IOD) DIAGNOSIS
GENERAL INFORMATION
Ignition off draw refers to power being drained
from the battery with the ignition switch turned off.
A normal vehicle electrical system will draw from 5
to 20 milliamps. This is with the ignition switch in
the OFF position, and all non-ignition controlled cir-
cuits in proper working order. A vehicle that has not
been operated for approximately 20 days, may dis-
charge the battery to an inadequate level. Battery
drain should not exceed approximately 20 MA (20
milliamps = 0.020 amps).
The 20 MA are needed to supply PCM memory,
digital clock memory, and ETR (electronically tuned
radio) memory.
Excessive battery drain is caused by items left
turned on, internally shorted generator, or intermit-
tent short in wiring.
If the IOD is over 20 milliamperes, the defect must
be found and corrected before replacing a battery. In
most cases the battery can be charged and returned
to service.
When a vehicle will not be used for 20 days or
more (stored), remove IOD fuse in the Power Distri-
bution Center to reduce battery discharging.
TEST PROCEDURE
Testing for higher amperage IOD must be per-
formed first to prevent damage to most milliamp
meters.
(1) Verify that all electrical accessories are OFF.
Turn off all lamps, remove ignition key, and close all
doors. If the vehicle is equipped with electronic acces-
sories (illuminated entry, high line radio), allow the
systems to automatically shut off (time out), up to 3
minutes.
(2) Determine that the underhood lamp is operat-
ing properly, then disconnect or remove bulb.
(3) Disconnect negative cable from battery.
(4) Connect a typical 12-volt test lamp (low watt-
age bulb) between the negative cable clamp and the
battery negative terminal. If equipped with security
alarm, cycle the key in the door to turn off the flash-ing lights. Make sure that the doors remain closed so
that illuminated entry is not activated.
The test lamp may light brightly for up to 3 min-
utes or may not light at all (depending on the elec-
trical equipment). The term brightly being used
throughout the following tests, implies the bright-
ness of the test lamp will be the same as if it were
connected across the battery.
The test lamp must be securely clamped to the neg-
ative cable and battery terminal. If the test lamp be-
comes disconnected during any part of the IOD test,
the electronic timer function will be activated and all
tests must be repeated.
If the ammeter circuit is broken the Security
Alarm Module will turn on parking lamps.
(5) After 3 minutes, the test lamp should turn OFF
or be DIMLY lit (depending on the electrical equip-
ment). If the test lamp remains brightly lit do not
disconnect it. Remove each fuse or circuit breaker
(refer to Group 8 - Wiring Diagrams) until test lamp
is either OFF or DIMLY lit. This will eliminate the
higher amperage draw.
If test lamp is still bright after disconnecting each
fuse and circuit breaker, disconnect the wiring har-
ness from the generator. Refer to Generator Test Pro-
cedures in this group. Do not disconnect the test
lamp.
After higher amperage IOD has been corrected, low
amperage IOD may be checked.
It is now safe to install milliamp meter to check for
low amperage IOD.
(6) With test lamp still connected securely, clamp
an ammeter between battery negative terminal and
negative battery cable.
Do not open any doors or turn on any electri-
cal accessories with the test lamp disconnected
or the meter may be damaged.
(7) Disconnect test lamp. The current draw should
not exceed 0.020 amp. If it exceeds 0.020 milliamps,
isolate each circuit by removing circuit breakers and
fuses. The meter reading drops once the high current
problem is found. Repair this section of the circuit,
whether it is a wiring short or component failure.
BATTERY CLASSIFICATIONS AND RATINGSTORQUE SPECIFICATIONS
8A - 8 BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICSJ

OPERATIONAL CHECK WITH VOLTMETER
When the ignition switch is turned to the ON po-
sition, battery potential will register on the voltme-
ter. During engine cranking a lower voltage will
appear on the meter. With the engine running, a
voltage reading higher than the first reading (igni-
tion in ON) should register.
DIAGNOSTIC PROCEDURES
If the indicator operates abnormally, or if an un-
dercharged or overcharged battery condition occurs,
the following procedures may be used to diagnose the
charging system.
Remember that an undercharged battery is often
caused by:
²accessories being left on overnight
²or by a defective switch which allows a bulb, such
as a liftgate or glove box light, to stay on (refer to
Ignition Off Draw Diagnosis).
VISUAL INSPECTION
²Inspect condition of battery cable terminals, bat-
tery posts, connections at engine block, starter motor
solenoid and relay. They should be clean and tight.
Repair as required.
²Inspect all fuses in the fuse block for tightness in
receptacles. They should be properly installed and
tight. Repair or replace as required.²Inspect the electrolyte level in the battery and add
water if necessary.
²Inspect generator mounting bolts for tightness. Re-
place or torque bolt as required. Refer to Torque
Specifications in Battery/Starter/Generator Service.
²Inspect generator drive belt condition and tension.
Tension or replace belt as required. Refer to Belt
Tension Specifications in Battery/Starter/Generator
Service.
²Inspect connection at generator B+ output. It
should be clean and tight. Repair as required.
GENERATOR OUTPUT WIRE RESISTANCE
TEST
Generator output wire resistance test will show
amount of voltage drop across generator output wire
between generator battery terminal and battery pos-
itive post.
PREPARATION
(1) Before starting test make sure vehicle has a
fully charged battery. Test and procedures on how to
check for a fully charged battery are shown in Bat-
tery Test Procedures.
(2) Turn OFF ignition switch.
(3) Disconnect negative cable from battery.
(4) Disconnect generator output wire from genera-
tor output battery terminal.
Fig. 2 Generator Output Wire Resistance Test (Typical)
JBATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS 8A - 15

INSTRUMENT PANEL AND GAUGES
GROUP INDEX
page page
INSTRUMENT PANEL AND GAUGESÐXJ..... 1INSTRUMENT PANEL AND GAUGESÐYJ.... 14
INSTRUMENT PANEL AND GAUGESÐXJE
CONTENTS
page page
INSTRUMENT CLUSTER DIAGNOSIS........ 3
INSTRUMENT CLUSTER GENERAL INFORMATION.. 1
INSTRUMENT CLUSTER SERVICE PROCEDURES... 5
SPECIFICATIONS....................... 13
INSTRUMENT CLUSTER GENERAL INFORMATION
INDEX
page page
4WD Indicator Lamp........................ 2
Anti-Lock Brake Indicator Lamp............... 2
Brake Indicator Lamp....................... 2
Coolant Temperature Gauge................. 1
Coolant Temperature Indicator Lamp........... 1
Fuel Gauge.............................. 2
Low Fuel Warning Lamp..................... 2Malfunction Indicator Lamp (Check Engine)...... 2
Oil Pressure Gauge....................... 1
Oil Pressure Indicator Lamp.................. 1
Speedometer/Odometer System.............. 2
Tachometer.............................. 2
Upshift Indicator Lamp...................... 2
Voltmeter............................... 1
With the ignition switch in the ON or START posi-
tion, voltage supplied to the instrument cluster is lim-
ited by fuse #17. The voltage is supplied to all the
gauges and indicator lamps through the instrument
cluster printed circuit.
With the ignition switch in the OFF position, volt-
age is not supplied to the instrument cluster and the
gauges do not indicate any vehicle condition.
VOLTMETER
The voltmeter measures battery or generator out-
put voltage, whichever is greater.
OIL PRESSURE GAUGE
The oil pressure gauge pointer position is controlled
by a magnetic field created by electrical current flow
through the coils within the gauge. A change in current
flow will change the magnetic field which changes the
pointer position. The oil pressure sender is a variable
resistor that changes electrical resistance with a change
in oil pressure (values shown in Specifications chart).
OIL PRESSURE INDICATOR LAMP
Voltage is supplied to one side of the indicator bulb
and the oil pressure switch is connected to the other
side. When oil pressure is too low the switch closes
providing a path to ground, and the indicator bulb
lights.
COOLANT TEMPERATURE GAUGE
The coolant temperature gauge pointer position is
controlled by a magnetic field created by electrical
current flow through the coils within the gauge. A
change in current flow will change the magnetic field
which changes the pointer position. The coolant tem-
perature sensor is a thermistor that changes electri-
cal resistance with a change in coolant temperature
(values shown in Specifications chart).
COOLANT TEMPERATURE INDICATOR LAMP
Voltage is supplied to one side of the indicator bulb
and the coolant temperature switch is connected to the
JINSTRUMENT PANEL AND GAUGES 8E - 1

INSTRUMENT CLUSTER DIAGNOSIS
INDEX
page page
4WD Indicator Inoperative................... 4
Anti-Lock Indicator......................... 4
Brake Indicator Inoperative.................. 4
Coolant Temperature Gauge Inoperative........ 3
Coolant Temperature Indicator Inoperative....... 3
Fuel Gauge Inoperative..................... 3
Gauges and Indicators Inoperative............ 3
Instrument Panel Lamps.................... 4
Low Fuel Warning Inoperative................ 4
Low Washer Indicator Inoperative............. 4Malfunction Indicator Lamp (Check Engine)...... 4
Oil Pressure Gauge Inoperative............... 3
Oil Pressure Indicator Inoperative............. 3
Radio/Clock Illumination.................... 4
Seat Belt Indicator........................ 4
Speedomete/Odometer Inoperative............. 3
Tachometer Inoperative..................... 3
Upshift Indicator Inoperative................. 4
Voltmeter Inoperative....................... 3
SPEEDOMETER/ODOMETER INOPERATIVE
(1) Check for continuity in the wire between the
vehicle speed sensor and cluster connector pin A5.
(2) With the ignition switch in the ON position,
check for battery voltage across pin A8 (B+) and pin
B2 (ground).
(3) Perform vehicle speed sensor test. Refer to the
appropriate vehicle Diagnostic Test Procedures man-
ual.
(4) If all the previous tests prove good, replace
speedometer/odometer.
GAUGES AND INDICATORS INOPERATIVE
(1) Remove and inspect fuse #17. Replace as re-
quired.
(2) Measure resistance at instrument cluster con-
nector terminal A3. Meter should read zero ohms. If
not, repair open to ground.
VOLTMETER INOPERATIVE
(1) Turn ignition switch to ON. Voltmeter should
read battery voltage. If not, go to step 2.
(2) Measure voltage at instrument cluster connec-
tor terminal A8. Meter should read battery voltage.
If OK, replace meter. If not, repair open to fuse #17.
OIL PRESSURE GAUGE INOPERATIVE
(1) Turn ignition switch to ON.
(2) Disconnect oil pressure sender connector (Fig.
1). Needle goes to H. If not, go to step 3.
(3) Touch oil pressure sender connector to ground.
Needle goes to L. If OK, replace sender. If not, repair
open to gauge (instrument cluster connector terminal
B7).
OIL PRESSURE INDICATOR INOPERATIVE
(1) Turn ignition switch to ON.
(2) Touch oil pressure switch connector to ground.
Lamp should light. If OK, replace switch. If bulb is
OK, repair open to instrument cluster connector ter-
minal B7.
COOLANT TEMPERATURE GAUGE INOPERATIVE
(1) Turn ignition switch to ON.
(2) Disconnect coolant temperature sender connec-
tor. Needle goes to C. If not, go to step 3.
(3) Touch coolant temperature sender connector to
ground. Needle goes to H. If OK, replace sender. If
not, repair open to gauge (instrument cluster connec-
tor terminal A1).
COOLANT TEMPERATURE INDICATOR
INOPERATIVE
(1) Turn ignition switch to ON.
(2) Touch coolant temperature indicator connector
to ground. Lamp should light. If OK, replace switch.
If bulb is OK, repair open to instrument cluster con-
nector terminal A1.
TACHOMETER INOPERATIVE
Tachometer input is from the Powertrain Control
Module pin 43. Use the DRB scan tool to test.
FUEL GAUGE INOPERATIVE
(1) Turn ignition switch to ON.
(2) Disconnect fuel gauge sender connector. Needle
should go to E.
Fig. 1 Oil Pressure Sending UnitÐ4.0L
JXJ INSTRUMENT PANEL AND GAUGES 8E - 3

(3) Connect a jumper between terminal A and B on
the body half of the fuel gauge sender connector. The
gauge should move to F. If gauge is OK, replace
sender. If not, go to step 4.
(4) Measure resistance of sender. Meter should
read 105 to 5 ohms. If OK, go to step 5. If not, re-
place sender.
(5) Check for an open between sender connector
and gauge. If OK, replace gauge. If not, repair open
to gauge.
LOW FUEL WARNING INOPERATIVE
(1) Turn ignition switch to ON.
(2) Disconnect terminal B1 of the instrument clus-
ter connector. Wait at least 10 seconds. Lamp (LED)
should light. If OK, replace sender. If not, replace
low fuel warning module.
UPSHIFT INDICATOR INOPERATIVE
(1) Turn ignition switch to ON.
(2) Ground pin 7 of connector B. Lamp should
light. If not, replace bulb. If OK, continue with
step 3.
(3) Turn ignition switch to OFF. Check for conti-
nuity between connector B pin 2 and pin 54 of the
Powertrain Control Module. If OK, replace PCM. If
not, repair open.
BRAKE INDICATOR INOPERATIVE
(1) Turn ignition switch to ON. Apply parking
brake, brake warning switch connector unplugged.
(2) Jumper brake warning switch connector termi-
nal B to ground. Lamp should light. If bulb is OK,
repair open to indicator.
(3) Turn ignition switch to OFF. Measure resis-
tance between brake warning switch connector ter-
minal A and ground. Meter should read zero ohms. If
OK, check switch and/or brake system. If not, repair
open to park brake switch ground.
4WD INDICATOR INOPERATIVE
(1) Apply parking brake, start engine, vehicle in
4WD Lock or 4WD.
(2) Unplug switch and touch harness side of wire
to ground. Lamp should light. If OK, check switch
operation, replace if bad. If bulb is OK, repair open
to indicator.
LOW WASHER INDICATOR INOPERATIVE
(1) Turn ignition switch to ON.
(2) Jumper 12 volts to fluid level switch connector
terminal B. Lamp should light. If not, go to step 3.
(3) Measure resistance between terminal B and
ground. Meter should read zero ohms. If not, repair
open to bulb. If OK, go to step 4.
(4) Measure voltage at fluid level switch connector
terminal A. Meter should read battery voltage. If
OK, replace switch. If not, repair open to fuse.
MALFUNCTION INDICATOR LAMP (CHECK ENGINE)
(1) Turn ignition switch to ON.
(2) Jumper Powertrain Control Module terminal 2
to ground. Lamp should light. If bulb is OK, check
for open to instrument cluster connector terminal 2.
ANTI-LOCK INDICATOR
(1) Turn ignition switch to ON.
(2) Jumper instrument cluster connector terminal
6 to ground. Lamp should light. If bulb is OK, check
wiring for an open to module. Refer to Group 5 -
Brakes.
SEAT BELT INDICATOR
Jumper instrument cluster connector terminal 15
to 12 volts. Lamp should light. If not, replace bulb. If
OK, check wiring for an open to buzzer module. Re-
fer to Group 8U - Chime/Buzzer Warning Systems.
RADIO/CLOCK ILLUMINATION
With the ignition switch in ACCESSORY or ON,
power comes from the radio fuse. It then goes
through the normally closed contacts of the radio il-
lumination relay to the radio at connector terminal
11.
Pulling the headlamp switch to ON energizes the
radio illumination relay. This closes the normally
open contacts of the relay, and the brightness for the
radio display is controlled by the headlamp switch
rheostat. The back-lighting for the radio is also con-
trolled by the headlamp rheostat through radio con-
nector terminal 10.
Refer to Group 8F - Audio Systems, for radio illu-
mination relay diagnosis.
INSTRUMENT PANEL LAMPS
Voltage is supplied at all times from the 40 amp
Maxi fuse (located in the Power Distribution Center)
through the park lamps fuse to the headlamp switch.
The circuit continues through the instrument lamps
fuse to the individual instrument panel lamps to
ground. Lamp brightness is controlled by turning the
headlamp switch knob.
DIAGNOSIS
(1) Turn parking lamps ON.
(2) Check park lamps fuse. Replace as required.
(3) Check instrument lamps fuse. Replace as re-
quired.
(4) Measure voltage at battery side of instrument
lamps fuse with rheostat turned counterclockwise to
clockwise (LO to HI). Meter should read zero volts to
battery voltage. If not, replace headlamp switch.
(5) Measure resistance at ground side of instru-
ment lamps fuse with parking lamps OFF. Meter
should read almost zero ohms (except bulb filament).
If not, repair open to ground. If zero ohms, 12 volt
supply wire from fuse is shorted to ground, repair short.
8E - 4 XJ INSTRUMENT PANEL AND GAUGESJ

INSTRUMENT PANEL AND GAUGESÐYJE
CONTENTS
page page
GAUGE PACKAGE DIAGNOSIS............ 22
GAUGE PACKAGE GENERAL INFORMATION . 22
GAUGE PACKAGE SERVICE PROCEDURES . . 24
INSTRUMENT CLUSTER DIAGNOSIS....... 14INSTRUMENT CLUSTER GENERAL INFORMATION.14
INSTRUMENT CLUSTER SERVICE PROCEDURES.. 17
SPECIFICATIONS....................... 27
INSTRUMENT CLUSTER GENERAL INFORMATION
SPEEDOMETER/ODOMETER SYSTEM
The speedometer/odometer system consists of an
electric speedometer and pushbutton reset odometer
mounted in the cluster. The system also includes the
wire harness from the cluster to the vehicle speed
sensor at the transmission, and the adapter and pin-
ion in the transmission. A signal is sent from a
transmission mounted vehicle speed sensor to the
speedometer/odometer circuitry through the wiring
harness. Refer to Group 21 - Transmission for select-
ing the proper pinion, and selecting and indexing the
proper adapter.
TACHOMETER
The tachometer displays the engine speed (RPM).
With the engine running, the tachometer receives anengine speed signal from the Powertrain Control
Module pin 43 (values shown in Specifications chart).
INDICATOR LAMPS
The Brake, Upshift (2.5L with 5 speed transmis-
sion except California), and Malfunction Indicator
(Check Engine) lamps are located in the indicator
lamp panel above the steering column. The lamps
share a common battery feed connection through the
ignition switch and fuse #9.
The turn signals, high beam indicator, seat belt re-
minder, hazard lamp, master lighting and illumina-
tion bulbs are supplied battery voltage through
various switches and share a common ground.
INSTRUMENT CLUSTER DIAGNOSIS
INDEX
page page
Brake Indicator Lamp...................... 16
DiagnosingÐAll Lamps Out................. 16
Instrument Panel Illumination Lamps.......... 16
Malfunction Indicator Lamp (Check Engine)..... 16Seat Belt Reminder Lamp................... 16
Speedometer............................ 14
Tachometer............................. 14
Upshift Indicator Lamp..................... 16
SPEEDOMETER
(1) Raise vehicle.
(2) Disconnect the vehicle speed sensor connector.
(3) Connect a voltmeter between the black wire
pin of the connector and ground.
(4) Turn the ignition switch to the ON position.
(5) Check for approximately 5 volts. If OK, per-
form vehicle speed sensor test. Refer to the appropri-
ate Powertrain Diagnostic Procedures manual. If not
OK, continue with step 6.
(6) Turn ignition switch to OFF position.(7) Check continuity between vehicle speed sensor
connector and terminal 13 of instrument cluster con-
nector. If OK, replace speedometer. If not OK, repair
open circuit.
TACHOMETER
(1) Tachometer input is from the Powertrain Con-
trol Module (PCM) pin 43. Use the DRB scan tool to
perform actuator test. If OK, continue with step 2. If
not, replace PCM.
(2) Check for continuity between cluster connector
pin 12 and PCM pin 43. If OK, replace tachometer. If
not, repair open circuit.
8E - 14 YJ INSTRUMENT PANEL AND GAUGESJ

DIAGNOSINGÐALL LAMPS OUT
(1) Inspect fuse #9. Replace as required.
(2) Measure voltage at instrument cluster connec-
tor terminal 20. Meter should read zero ohms. If not,
repair open to ground.
UPSHIFT INDICATOR LAMP
Vehicles equipped with manual transmissions have
an optional upshift indicator lamp. The lamp is con-
trolled by the PCM. The lamp lights to indicate when
the driver should shift to the next highest gear for best
fuel economy. The PCM will turn the lamp off after 3 to
5 seconds if the upshift is not performed. The lamp will
remain off until the vehicle stops accelerating and is
brought back to the range of lamp operation or shifted
into another gear.
The indicator lamp is normally illuminated when
the ignition switch is turned ON and it is turned off
when the engine is started. The lamp will be lighted
during engine operation according to engine speed
and load.
(1) Turn ignition switch to ON.
(2) Ground pin 2 of cluster connector. Lamp should
light. If not, replace bulb. If OK, continue with step 3.
(3) Turn ignition switch to OFF. Check for conti-
nuity between cluster connector pin 2 and pin 54 of
the PCM. If not, repair open. If OK, refer to DRB
scan tool actuator test of upshift indicator.
BRAKE INDICATOR LAMP
The brake indicator is a dual function lamp. It will in-
dicate an unequal pressure condition in the split brake
hydraulic system and it also will indicate when the park-
ing brake is engaged. Separate switches are used for each
indicator lamp function. A switch mounted on the brake
pedal assembly will close a ground circuit whenever the
parking brakes are applied. A second switch is installed
in the brake hydraulic lines near the master cylinder. If
the switch is balanced by equal pressure on both ends of
the switch valve, the valve remains centered and the
lamp remains off. If the valve is shifted by unequal pres-
sure between the front or rear brake hydraulic systems,
the lamp circuit is connected to ground. To make sure
the brake lamp is functional before the vehicle is driven,
it is illuminated through a ground circuit when the igni-
tion switch is turned to the START position.
(1) Turn ignition switch to ON.
(2) Ground pin 1 of the cluster connector. Lamp
should light. If not, replace bulb. If OK, continue
with step 3.
(3) Turn ignition switch to OFF. Check for continuity to
park brake switch and brake warning switch.
MALFUNCTION INDICATOR LAMP (CHECK ENGINE)
The Malfunction Indicator Lamp (Check Engine) il-
luminates each time the ignition switch is turned
ON and stays on for 3 seconds as a bulb test.If the PCM receives an incorrect signal or no signal
from certain sensors or emission related systems the
lamp is turned on (pin 32 of PCM). This is a warning
that the PCM has recorded a system or sensor mal-
function. In some cases when a diagnostic fault is de-
clared the PCM will go into a limp-in mode in an
attempt to keep the system operating. It signals an
immediate need for service.
The lamp also can be used to display diagnostic
trouble codes (DTC). Cycle the ignition switch ON,
OFF, ON, OFF, ON within 5 seconds. This will allow
any DTC's stored in the PCM memory to be dis-
played in a series of flashes representing digits.
(1) Turn ignition switch to ON.
(2) Ground pin 4 of cluster connector. Lamp should
light. If not, replace bulb. If OK, continue with step 3.
(3) Turn ignition switch to OFF. Check for conti-
nuity between cluster connector pin 4 and PCM cav-
ity 32. If OK, replace PCM. If not, repair open.
SEAT BELT REMINDER LAMP
Apply 12 volts to terminal 16 of cluster connector.
Lamp should light. If not, replace bulb. If OK, check
wiring for an open to buzzer module. Refer to Group
8U - Chime/Buzzer Warning Systems.
INSTRUMENT PANEL ILLUMINATION LAMPS
The instrument panel illumination lamps share
two common connections. There is a splice after fuse
#10 that connects the lamps to battery feed. There is
also a splice that connects all lamps to ground. Be-
cause they share these common connection points in
a parallel circuit, the illumination lamps will all
come on at the same time. It also means one or more
lamps can be out without affecting the operation of
the other lamps.
On the battery side of the circuit, the headlamp
switch illumination rheostat/switch and panel lamps
fuse receive battery feed in series from the park/tail
fuse. In the park lamp position, the headlamp switch
completes the circuit from the park/tail fuse to the il-
lumination rheostat/switch and panel lamps fuse.
The illumination rheostat contains a variable resis-
tor that allows the driver to vary illumination inten-
sity from off to full brightness.
DIAGNOSIS
(1) Turn parking lamps ON.
(2) Check fuse #10. Replace as required.
(3) Measure voltage at battery side of fuse #10
with rheostat turned counterclockwise to clockwise
(LO to HI). Meter should read zero volts to battery
voltage. If not, replace headlamp switch.
(4) Measure resistance at ground side of fuse #10
with parking lamps OFF. Meter should read almost
zero ohms (except bulb filament). If not, repair open
to ground. If zero ohms, 12 volt supply wire from fuse
is shorted to ground, repair short.
8E - 16 YJ INSTRUMENT PANEL AND GAUGESJ

GAUGE PACKAGE GENERAL INFORMATION
The gauge package contains 4 gauges and the 4
wheel drive indicator. The gauges have a common
battery feed from fuse #9 and ignition switch. Al-
though they have separate power sources, the 4
gauges share a common ground connection.
The voltmeter indicates electrical system voltage.
When the engine is not running, the voltage regis-
tered is from the battery. After the engine is started,
charging system voltage is indicated. In the gauge
package, the voltmeter forms a parallel connectionacross the battery feed and ground.
The remaining gauges - oil pressure, fuel and cool-
ant temperature - are connected to individual sender
units. Variable resistors in the senders will change
the amount of current allowed to flow through the
gauge coils. As current flow through the coils varies,
the position of the indicator needle also will vary.
The 4 gauges are connected to battery feed, ground
and the sender units through a printed circuit
mounted on the back of the gauge housing.
GAUGE PACKAGE DIAGNOSIS
ALL GAUGES INOPERATIVE (Fig. 15)
(1) Check the fuse #9. Replace as required.
(2) Turn ignition switch to ON and measure volt-
age at battery side of fuse #9. Meter should read bat-
tery voltage. If not, repair open from ignition switch.
(3) Unplug gauge package connector from gauge
package.
(4) Turn ignition switch to OFF and measure resis-
tance from instrument cluster connector terminals 1
and 13 to a clean chassis ground. Meter should read
zero ohms. If not, repair open to ground.
(5) Turn ignition switch to ON and measure volt-
age at instrument cluster connector terminals 2 and
12. Meter should read battery voltage. If not, repair
open from fuse panel.
ONE GAUGE INOPERATIVE
Does not apply to voltmeter.
OIL PRESSURE SENDER
(1) Turn ignition switch to ON.
(2) Unplug oil pressure sender connector from oil
pressure sender.
(3) Touch connector to engine block (ground).
Gauge should read at low end of scale.
(4) When connector is NOT touching ground (open
circuit) gauge should read at high end of scale. If OK
replace sender. If not, proceed with step 5.
(5) Check circuit between sender and gauge for an
open. Repair as required. If wiring is OK, replace
gauge.
COOLANT TEMPERATURE SENDER
(1) Turn ignition switch to ON.
(2) Unplug coolant temperature sender connector
from coolant temperature sender.
(3) Touch connector to engine block (ground).
Gauge should read at high end of scale.
(4) When connector is NOT touching ground (open
circuit) gauge should read at low end of scale. If OK
replace sender. If not, proceed with step 5.
(5) Check circuit between sender and gauge for an
open. Repair as required. If wiring is OK, replace
gauge.
FUEL GAUGE SENDER
(1) Turn ignition switch to ON.
(2) Separate fuel gauge sender connector from fuel
gauge sender near tank.
(3) Ground the center wire of the body harness
side of the connector. The gauge should read at low
end of scale. If OK, check sending unit (step 4). If
not, check circuit between connector and gauge. Re-
pair as required. If circuit is OK, replace gauge.
(4) Turn ignition switch to OFF.
(5) Measure resistance from fuel gauge sender con-
nector center terminal to a clean chassis ground.
Meter readings should correspond to those shown in
Specifications. If not OK, replace sender. If OK, re-
pair open from fuel gauge sender connector to
ground.
PRINTED CIRCUIT
(1) Turn ignition switch to ON.
(2) Unplug gauge package connector from gauge
package.
(3) Measure resistance from gauge package termi-
nal 12 (fuel and coolant temperature gauge) or from
terminal 2 (voltmeter and oil pressure gauge) to
gauge battery terminal. Meter should read zero
ohms. If not, replace/repair printed circuit.
(4) Measure resistance from gauge package termi-
nal 13 (fuel and coolant temperature gauge) or from
terminal 1 (voltmeter and oil pressure gauge) to
gauge ground terminal. Meter should read zero
ohms. If not, replace/repair printed circuit. If zero
ohms, replace gauge.
GAUGE CALIBRATION VALUES
Use the charts in Specifications. The calibration of
the gauge can be checked. If the indicator needle is
not in the correct position, replace the gauge.
4WD INDICATOR
The four-wheel drive indicator lamp circuit is com-
pleted by the Command-Trac switch located below
the battery.
8E - 22 YJ INSTRUMENT PANEL AND GAUGESJ

AUDIO SYSTEMS
CONTENTS
page page
GENERAL INFORMATION.................. 1
RADIO ANTENNA........................ 8XJ SERVICE PROCEDURES................ 4
YJ SERVICE PROCEDURES................ 6
GENERAL INFORMATION
DESCRIPTION
Each radio receives ignition feed from an ignition
switch controlled fuse. There is an additional in-line
fuse in the back of the radio chassis. The in-line fuse
will blow in the event an internal short occurs.
The electronically tuned radio (ETR)/cassette
models protect the vehicle from a radio failure
with an in-line fuse located in the rear of the ra-
dio chassis (Fig. 1).
XJ/YJ vehicles are equipped with an Ignition-Off
Draw (IOD) fuse that is removed when the vehicles
are shipped from the factory. This fuse is in the
Power Distribution Center to prevent battery dis-
charge during storage. For specific location refer to
Group 8W - Wiring Diagrams.
The IOD fuse is in the radio memory circuitry and
should be checked if the memory (time or radio sta-
tion programming) is inoperative.
All radios are connected to the radio illumination
relay. When the ignition switch is in ON or ACCES-
SORY and the radio illumination relay remains de-
energized, the radio receives battery voltage via the
relay from the:
²(20 amp #7 fuse YJ)
²(15 amp #2 fuse XJ).
The radio illumination relay is energized when the
headlamp switch is used to turn on the parklamps or
headlamps. Battery voltage is switched to the dimdisplay input of the radio through the relay contacts.
The radio panel illumination is dimmed for night
driving.
The ETR models require an additional battery feed
connection to the (10 amp #F16 fuse-YJ), (10 amp
#9 fuse-XJ) to retain the radio's memory when the
ignition switch is turned OFF.
ETR models are self-compensating. A radio
trimmer adjustment is not required.
DIAGNOSIS
RADIO INOPERATIVE
Turn ignition switch to ON
²Inspect the (#7-YJ), (#2-XJ) fuse and replace if
necessary.
²Measure voltage at battery side of the fuse. There
should be 12 volts. If not, repair open from ignition
switch.
²Inspect in-line fuse at rear of radio and replace if
necessary.
Turn ignition switch to OFF.
²Disconnect radio connector. Measure resistance
from radio ground pin to a clean chassis ground.
There should be zero ohms. If not, repair open be-
tween radio connector and ground.
NO AUDIO OUTPUT ON ONE OR MORE
SPEAKERS
Refer to Radio Connector Pins.
FRONT SPEAKERS
²Radio OFF, radio connector disconnected. Measure
resistance between radio left front feed and return
connector pins. Measure between right front feed and
return connector pins. The meter should read 5 to 8
ohms. If the meter reading is correct, remove radio
for service. If not, repair wiring or replace speakers
as required.
Fig. 1 In-Line Fuse Location
JAUDIO SYSTEMS 8F - 1