1994 JEEP CHEROKEE check engine

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

other side. When coolant temperature is too high the
switch closes providing a path to ground, and the indi-
cator bulb lights.
TACHOMETER
The tachometer displays the engine speed (RPM).
With the engine running, the tachometer receives an
engine speed signal from the Powertrain Control
Module pin 43 (values shown in Specifications chart).
SPEEDOMETER/ODOMETER SYSTEM
The speedometer/odometer system consists of an elec-
tric speedometer and pushbutton reset odometer
mounted in the cluster. The system also includes the
wire harness from the cluster to the vehicle speed sen-
sor at the transmission, and the adapter and pinion in
the transmission. A signal is sent from a transmission
mounted vehicle speed sensor to the speedometer/odom-
eter circuitry through the wiring harness. Refer to
Group 21 - Transmission for selecting the proper pinion,
and selecting and indexing the proper adapter.
FUEL GAUGE
The fuel 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 po-
sition. The fuel level sender is a variable resistor that
changes electrical resistance with a change of the level
of fuel in the tank (values shown in Specifications
chart).
LOW FUEL WARNING LAMP
The low fuel warning lamp will light when the fuel
level falls below approximately 4 gallons. A low fuel
warning module controls when the lamp will light.
When the module senses 66.5 ohms or less from the
fuel level sender for 10 continuous seconds, the lamp
will light. The lamp will remain on until the module
senses 63.5 ohms or more from the fuel level sender
for 20 continuous seconds.
UPSHIFT INDICATOR LAMP
Vehicles equipped with manual transmissions have an
optional upshift indicator lamp. The lamp is controlled
by the Powertrain Control Module. The lamp lights to
indicate when the driver should shift to the next high-
est gear for best fuel economy. The Powertrain Control
Module 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 is turned off
when the engine is started. The lamp will be lighted
during engine operation according to engine speed
and load.
BRAKE INDICATOR LAMP
The brake indicator lamp warns the driver that the
parking brake is applied or that hydraulic pressure in
the split brake system is unequal.
Voltage is supplied through the brake indicator
bulb to 3 switches. A path to ground for the current
is available if:
²The brake warning switch is closed (with unequal
brake system hydraulic pressures), or
²
The ignition switch is in the START position (to test
the bulb), or
²The park brake switch is closed (with the parking
brake applied).
ANTI-LOCK BRAKE SYSTEM (ABS) INDICATOR
LAMP
The anti-lock brake system (ABS) lamp lights to in-
dicate a system self-check is in process at vehicle
start-up. If light remains on after start-up or comes
on and stays on while driving, it may indicate that
the ABS system has detected a malfunction or has
become inoperative.
4WD INDICATOR LAMP
COMMAND-TRAC 4WD
The PART TIME lamp lights when the vehicle is en-
gaged in four-wheel drive mode. Voltage is supplied to
one side of the indicator bulb. A switch in the transfer
case area is connected to the other side of the indicator
bulb. When the switch is closed, a path to ground is pro-
vided and the indicator bulb lights.
SELECT-TRAC 4WD
The four-wheel drive icon or FULL TIME lamp
lights when the vehicle is engaged in full time four-
wheel drive mode. The PART TIME lamp lights when
the vehicle is in part time four-wheel drive mode.
Voltage is supplied to one side of the indicators.
Switches in the transfer case area are connected to
the other side of the indicator bulbs. When a switch
is closed, a path to ground is provided and the indi-
cator bulb lights.
MALFUNCTION INDICATOR LAMP (CHECK ENGINE)
The Malfunction Indicator Lamp (Check Engine)
lights 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 trouble
code is declared the PCM will go into a limp-in mode
in an attempt to keep the system operating. It sig-
nals 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 trouble codes stored in the PCM memory to be
displayed in a series of flashes representing digits.
8E - 2 XJ INSTRUMENT PANEL AND GAUGESJ

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

REAR SPEAKERS
²Radio OFF, radio connector disconnected. Measure
resistance between radio left rear feed and return
connector pins. Measure between right rear feed and
return connector pins. The meter should read 5 to 8
ohms. If meter reading is correct remove radio for
service. If not, repair wiring or replace speakers as
required.
DISTORTED AUDIO OUTPUT ON ONE OR
MORE SPEAKERS
²With the radio ON, substitute known good speaker
or speakers. If the sound is still distorted, remove ra-
dio for service.
WEAK OR NO RECEPTION; NO AUDIO
OUTPUT; BACKGROUND NOISE PRESENT
Ignition switch in ON, radio ON.
²Inspect antenna cable and connector at radio and
tighten or repair as necessary.
²Unplug coax cable and connectors from radio. Mea-
sure resistance from center conductor to coaxial
shield. The meter should read infinite resistance
(open). If it does not, replace antenna assembly.
²Measure resistance of antenna mast to tip of cen-
ter conductor at radio end of cable. The meter should
read 0 to 0.5 ohms. If it does not, replace lead-in ca-
ble or antenna assembly.
²Measure resistance from coaxial shield to chassis
ground (vehicle body). The meter should read zero
ohms. If it does not, ground antenna base to vehicle
body, or replace antenna assembly as required
For all problems with no or low audio output
not resolved by these tests, remove radio for ser-
vice.
MEMORY DOES NOT OPERATE
²Inspect (F16 in Power Distribution Center-YJ),
(#9 in Fuse Panel-XJ) fuse and replace if necessary.
²Measure voltage at battery side of previously ref-
erenced fuse. There should be 12 volts at battery side
of fuse. If not, check the Maxi fuse.
Refer to Group 8W - Wiring Diagrams.
²Measure voltage at radio connector pin 4. There
should be 12 volts. If meter reading is correct, re-
move radio for service. If not, repair open from fuse.
RADIO DISPLAY ILLUMINATION (PARKLAMPS
AND HEADLAMPS OPERATING NORMALLY)
Headlamp switch OFF, radio ON.
²Measure voltage at radio connector pin 10. There
should be 12 volts. If not, go to next step. If OK, re-
move radio for repair by authorized outlet.
²Measure voltage at illumination relay pin 3. There
should be 12 volts. If 12 volts present, replace illumi-
nation relay. If not, repair open in circuit.RADIO DISPLAY ILLUMINATION DIMMING CIRCUIT
Turn headlamp switch to PARKLAMPS for
voltage tests; turn headlamp switch to OFF for
resistance tests.
²Separate relay connector from radio illumination
relay. Measure resistance from relay connector pin 2
to a clean chassis ground. The meter should read
zero ohms. If not, repair open between relay connec-
tor and ground.
²Measure voltage at radio illumination relay pin 5.
There should be battery voltage. If not repair open
from headlamp switch.
²Measure voltage at radio illumination relay pin 4.
Voltage should vary with dimmer switch. If OK, go
to next step. If not, repair open circuit between pin 4
and interior lamp rheostat.
²Measure voltage at radio illumination relay pin
10. Voltage should vary with dimmer switch. If OK,
remove radio for repair by authorized outlet. If not,
replace radio illumination relay.NOISE INTERFERENCE CHANGES WITH
ENGINE SPEED
²Inspect connections at: generator, ignition module,
antenna coaxial ground, radio ground, body to engine
block ground (braided ground strap). Repair as re-
quired.
RADIO NOISE DIAGNOSIS
8F - 2 AUDIO SYSTEMSJ