electrical wiring JEEP GRAND CHEROKEE 2002 WJ / 2.G Owner's Manual

HEATED SEAT SENSOR
DESCRIPTION
The heated seat temperature sensor is a Negative
Temperature Coefficient (NTC) thermistor. One tem-
perature sensor is used for each seat. This tempera-
ture sensor is located in the seat cushion heating
element on all models.
The heated seat temperature sensor cannot be
repaired or adjusted and must be replaced if defec-
tive. The heated seat cushion element must be
replaced if the temperature sensor is defective. Refer
to the procedure in this section of the service man-
ual.
DIAGNOSIS AND TESTING - HEATED SEAT
SENSOR
For complete circuit diagrams, refer toWiring
Diagrams.
(1) Disconnect the Heated Seat Module (HSM) or
Memory Heated Seat Module (MHSM) C1 connector.
Check for continuity between the SEAT SENSOR 5V
SUPPLY circuit cavity and the seat cushion frame.
There should beNOcontinuity. If OK, go to Step 2.
If not OK, repair the shorted seat sensor 5V supply
circuit as required.
(2) Check for continuity between the SEAT SEN-
SOR 5V SUPPLY circuit cavity of the 4-way power
seat wire harness connector and the C1 connector for
the HSM or MHSM. There should be continuity. If
OK, go to Step 3. If not OK, repair the open seat sen-
sor 5V supply circuit as required.
(3) Connect the module electrical connector. Turn
system ON, using a voltmeter, backprobe the HSM or
MHSM C1 connector on the SEAT TEMPERATURE
SENSOR INPUT circuit cavity. Voltage should be
present (2-4 volts). If OK, proceed with testing the
other components in the heated seat system. If not
OK, refer to Heated Seat Module Diagnosis and Test-
ing in the electronic control modules section of this
manual.
REMOVAL
(1) For heated seat sensor replacement procedure
(Refer to 8 - ELECTRICAL/HEATED SEATS/
HEATED SEAT ELEMENT - REMOVAL).
PASSENGER HEATED SEAT
SWITCH
DESCRIPTION
The heated seat switches are mounted in the
instrument panel center lower bezel (Fig. 7), which is
located near the bottom of the instrument panel cen-
ter stack. The two three-position rocker-type
switches, one switch for each front seat, provide a
resistor multiplexed signal to the Body Control Mod-
ule (BCM) through separate hard wired circuits.
Each switch has an Off, Low, and High position so
that both the driver and the front seat passenger can
select a preferred seat heating mode. Each switch
has two Light-Emitting Diodes (LED), one each for
the Low position and the High position, which light
to indicate that the heater for the seat that the
switch controls is turned on. Each switch is also back
lit by a replaceable incandescent bulb.
The heated seat switches and their LEDs cannot
be repaired. If either switch or LED is faulty or dam-
aged, the entire switch unit must be replaced. The
incandescent switch illumination bulb and bulb
holder units are available for service replacement.
Fig. 7 HEATED SEAT SWITCHES
1 - HEATED SEAT SWITCHES
WJHEATED SEAT SYSTEM 8G - 15

HORN
TABLE OF CONTENTS
page page
HORN SYSTEM
DESCRIPTION..........................1
OPERATION............................2
DIAGNOSIS AND TESTING - HORN SYSTEM . . . 2
HORN
DESCRIPTION..........................3
OPERATION............................3
DIAGNOSIS AND TESTING - HORN..........3
REMOVAL.............................3
INSTALLATION..........................4
HORN RELAY
DESCRIPTION..........................4OPERATION............................4
DIAGNOSIS AND TESTING - HORN RELAY....4
REMOVAL.............................5
INSTALLATION..........................5
HORN SWITCH
DESCRIPTION..........................6
OPERATION............................6
DIAGNOSIS AND TESTING - HORN SWITCH . . . 6
REMOVAL.............................7
INSTALLATION..........................7
HORN SYSTEM
DESCRIPTION
A dual-note electric horn system is standard facto-
ry-installed equipment on this model. The standard
equipment horn system features one low-note horn
unit and one high-note horn unit. The horn system
allows the vehicle operator to provide an audible
warning of the presence or approach of the vehicle to
pedestrians and the drivers of other vehicles in near
proximity. The horn system uses a non-switched
source of battery current so that the system will
remain functional, regardless of the ignition switch
position.
The horn system can also be activated by the Body
Control Module (BCM). The BCM is programmed to
activate the horns in order to provide the following
features:
²Remote Keyless Entry (RKE) system lock
request audible verification (except export)
²RKE system panic mode audible alert
²Vehicle Theft Security System (VTSS) audible
alarm.
This vehicle also offers several customer program-
mable features, which allows the selection of several
optional electronic features to suit individual prefer-
ences. Refer to Overhead Console for more informa-
tion on the customer programmable feature options.
Customer programmable feature options affecting the
horn system include:
²Sound Horn on Lock- Allows the option of
having the horn sound a short chirp as an audible
verification that the RKE system received a valid
Lock request from the RKE transmitter, or having no
audible verification.The horn system includes the following compo-
nents:
²Clockspring
²Horns
²Horn relay
²Horn switch
Certain functions and features of the horn system
rely upon resources shared with other electronic
modules in the vehicle over the Programmable Com-
munications Interface (PCI) data bus network. The
PCI data bus network allows the sharing of sensor
information. This helps to reduce wire harness com-
plexity, internal controller hardware, and component
sensor current loads. At the same time, this system
provides increased reliability, enhanced diagnostics,
and allows the addition of many new feature capabil-
ities. For diagnosis of these electronic modules or of
the PCI data bus network, the use of a DRB scan
tool and the proper Diagnostic Procedures manual
are recommended.
The other electronic modules that may affect horn
system operation are as follows:
²Body Control Module (BCM)(Refer to 8 -
ELECTRICAL/ELECTRONIC CONTROL MOD-
ULES/BODY CONTROL/CENTRAL TIMER MODUL
- DESCRIPTION) for more information.
²Electronic Vehicle Information Center
(EVIC)(Refer to 8 - ELECTRICAL/OVERHEAD
CONSOLE/ELECTRONIC VEHICLE INFO CENTER
- DESCRIPTION) for more information.
(Refer to 8 - ELECTRICAL/RESTRAINTS/CLOCK-
SPRING - DESCRIPTION) for more information on
this component. Refer to the appropriate wiring
information. The wiring information includes wiring
diagrams, proper wire and connector repair proce-
dures, details of wire harness routing and retention,
WJHORN 8H - 1

CONDITION POSSIBLE CAUSES CORRECTION
HORN SOUNDS
CONTINUOUSLY1. Faulty horn relay. 1. Refer to Horn Relay for the proper horn relay
diagnosis and testing procedures. Replace the
horn relay or repair the shorted horn relay control
circuit, if required.
2. Faulty horn switch. 2. Refer to Horn Switch for the proper horn switch
diagnosis and testing procedures. Replace the
horn switch or repair the shorted horn switch
circuit, if required.
HORN
DESCRIPTION
The dual electromagnetic diaphragm-type horns
are standard equipment on this model. Both horns
are secured to a mounting bracket. The mounting
bracket is secured with a screw to the back side of
the right extension of the radiator closure assembly,
just ahead of the right front wheel house and below
the front wheel house extension. The two horns are
connected in parallel. Each horn is grounded through
its wire harness connector and circuit to an eyelet
secured to the right inner fender shield near the bat-
tery, and receives battery feed through the closed
contacts of the horn relay.
The horns cannot be repaired or adjusted and, if
faulty or damaged, they must be individually
replaced.
OPERATION
Within the two halves of the molded plastic horn
housing are a flexible diaphragm, a plunger, an elec-
tromagnetic coil and a set of contact points. The dia-
phragm is secured in suspension around its
perimeter by the mating surfaces of the horn hous-
ing. The plunger is secured to the center of the dia-
phragm and extends into the center of the
electromagnet. The contact points control the current
flow through the electromagnet.
When the horn is energized, electrical current
flows through the closed contact points to the electro-
magnet. The resulting electromagnetic field draws
the plunger and diaphragm toward it until that
movement mechanically opens the contact points.
When the contact points open, the electromagnetic
field collapses allowing the plunger and diaphragm to
return to their relaxed positions and closing the con-
tact points again. This cycle continues repeating at a
very rapid rate producing the vibration and move-
ment of air that creates the sound that is directed
through the horn outlet.
DIAGNOSIS AND TESTING - HORN
Refer to the appropriate wiring information. The
wiring information includes wiring diagrams, proper
wire and connector repair procedures, details of wire
harness routing and retention, connector pin-out
information and location views for the various wire
harness connectors, splices and grounds.
(1) Disconnect the wire harness connector(s) from
the horn connector receptacle(s). Measure the resis-
tance between the ground circuit cavity of the horn(s)
wire harness connector(s) and a good ground. There
should be no measurable resistance. If OK, go to Step
2. If not OK, repair the open ground circuit to ground
as required.
(2) Check for battery voltage at the horn relay out-
put circuit cavity of the horn(s) wire harness connec-
tor(s). There should be zero volts. If OK, go to Step 3.
If not OK, repair the shorted horn relay output cir-
cuit or replace the faulty horn relay as required.
(3) Depress the horn switch. There should now be
battery voltage at the horn relay output circuit cavity
of the horn(s) wire harness connector(s). If OK,
replace the faulty horns. If not OK, repair the open
horn relay output circuit to the horn relay as
required.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Raise and support the vehicle.
(3) Remove the lower front half of the inner liner
from the right front fender wheel house. (Refer to 23
- BODY/EXTERIOR/FRONT FENDER - REMOVAL).
(4) Reach through the front of the right front
fender wheel house opening to access and disconnect
the two right headlamp and dash wire harness con-
nectors from the horn connector receptacles (Fig. 1).
Be certain to disengage the connector lock tabs
before disconnecting them from the horn connector
receptacles.
(5) Remove the screw that secures the horn
mounting bracket to the right extension of the radi-
ator closure assembly.
WJHORN 8H - 3
HORN SYSTEM (Continued)

(6) Remove both horns and the mounting bracket
from the right extension of the radiator closure
assembly as a unit.
INSTALLATION
(1) Position both horns and the mounting bracket
onto the right extension of the radiator closure
assembly as a unit.
(2) Install and tighten the screw that secures the
horn mounting bracket to the right extension of the
radiator closure assembly. Tighten the screw to 11.3
N´m (100 in. lbs.).
(3) Reconnect the two right headlamp and dash
wire harness connectors to the horn connector recep-
tacles. Be certain to engage the connector lock tabs
after reconnecting them to the horn connector recep-
tacles.
(4) Install the lower front half of the inner liner to
the right front fender wheel house. (Refer to 23 -
BODY/EXTERIOR/FRONT FENDER - INSTALLA-
TION) for the procedure.
(5) Lower the vehicle.
(6) Reconnect the battery negative cable.
HORN RELAY
DESCRIPTION
The horn relay is a electromechanical device that
switches battery current to the horn when the horn
switch grounds the relay coil. The horn relay is
located in the Power Distribution Center (PDC) inthe engine compartment. If a problem is encountered
with a continuously sounding horn, it can usually be
quickly resolved by removing the horn relay from the
PDC until further diagnosis is completed. See the
fuse and relay layout label affixed to the inside sur-
face of the PDC cover for horn relay identification
and location.
The horn relay is a International Standards Orga-
nization (ISO) micro-relay. Relays conforming to the
ISO specifications have common physical dimensions,
current capacities, terminal patterns, and terminal
functions. The ISO micro-relay terminal functions
are the same as a conventional ISO relay. However,
the ISO micro-relay terminal pattern (or footprint) is
different, the current capacity is lower, and the phys-
ical dimensions are smaller than those of the conven-
tional ISO relay.
The horn relay cannot be repaired or adjusted and,
if faulty or damaged, it must be replaced.
OPERATION
The ISO relay consists of an electromagnetic coil, a
resistor or diode, and three (two fixed and one mov-
able) electrical contacts. The movable (common feed)
relay contact is held against one of the fixed contacts
(normally closed) by spring pressure. When the elec-
tromagnetic coil is energized, it draws the movable
contact away from the normally closed fixed contact,
and holds it against the other (normally open) fixed
contact.
When the electromagnetic coil is de-energized,
spring pressure returns the movable contact to the
normally closed position. The resistor or diode is con-
nected in parallel with the electromagnetic coil in the
relay, and helps to dissipate voltage spikes that are
produced when the coil is de-energized.
DIAGNOSIS AND TESTING - HORN RELAY
The horn relay (Fig. 2) is located in the Power Dis-
tribution Center (PDC) between the battery and the
right inner fender shield on the passenger side of the
engine compartment. If a problem is encountered
with a continuously sounding horn, it can usually be
quickly resolved by removing the horn relay from the
PDC until further diagnosis is completed. See the
fuse and relay layout label affixed to the inside sur-
face of the PDC cover for horn relay identification
and location. For complete circuit diagrams, refer to
the appropriate wiring information. The wiring infor-
mation includes wiring diagrams, proper wire and
connector repair procedures, details of wire harness
routing and retention, connector pin-out information
and location views for the various wire harness con-
nectors, splices and grounds.
Fig. 1 Horns Remove/Install
1 - RADIATOR CLOSURE ASSEMBLY
2 - HORNS AND MOUNTING BRACKET
3 - RIGHT HEADLAMP AND DASH WIRE HARNESS
CONNECTORS
8H - 4 HORNWJ
HORN (Continued)

HORN SWITCH
DESCRIPTION
A center-blow, normally open, resistive membrane-
type horn switch is secured in a plastic tray that is
inserted in a pocket sewn on the front of the driver
side airbag retainer strap. The horn switch is con-
cealed behind the driver side airbag module trim
cover in the center of the steering wheel. The switch
consists of two plastic membranes, one that is flat
and one that is slightly convex. These two mem-
branes are secured to each other around the perime-
ter. Inside the switch, the centers of the facing
surfaces of these membranes each has a grid made
with an electrically conductive material applied to it.
One of the grids is connected to a circuit that pro-
vides it with continuity to ground at all times. The
grid of the other membrane is connected to the horn
relay control circuit.
The steering wheel and steering column must be
properly grounded in order for the horn switch to
function properly. The horn switch and plastic tray
are serviced as a unit. If the horn switch is damaged
or faulty, or if the driver side airbag is deployed, the
horn switch and tray must be replaced as a unit.
OPERATION
When the center area of the driver side airbag trim
cover is depressed, the electrically conductive grids
on the facing surfaces of the horn switch membranes
contact each other, closing the switch circuit. The
completed horn switch circuit provides a ground for
the control coil side of the horn relay, which activates
the relay. When the horn switch is released, the
resistive tension of the convex membrane separates
the two electrically conductive grids and opens the
switch circuit.
DIAGNOSIS AND TESTING - HORN SWITCH
For complete circuit diagrams, refer to the appro-
priate wiring information. The wiring information
includes wiring diagrams, proper wire and connector
repair procedures, details of wire harness routing
and retention, connector pin-out information and
location views for the various wire harness connec-
tors, splices and grounds.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, REFER TO ELECTRICAL, RESTRAINTS
BEFORE ATTEMPTING ANY STEERING WHEEL,
STEERING COLUMN, OR INSTRUMENT PANEL
COMPONENT DIAGNOSIS OR SERVICE. FAILURE
TO TAKE THE PROPER PRECAUTIONS COULD
RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT
AND POSSIBLE PERSONAL INJURY.
(1) Disconnect and isolate the battery negative
cable. Remove the steering column opening cover
from the instrument panel.
(2) Check for continuity between the metal steer-
ing column jacket and a good ground. There should
be continuity. If OK, go to Step 3. If not OK, refer to
Steering, Column for proper installation of the steer-
ing column.
(3) Remove the driver side airbag module from the
steering wheel. Disconnect the horn switch wire har-
ness connectors from the driver side airbag module.
(4) Remove the horn relay from the Power Distri-
bution Center (PDC). Check for continuity between
the steering column half of the horn switch feed wire
harness connector and a good ground. There should
be no continuity. If OK, go to Step 5. If not OK,
repair the shorted horn relay control circuit to the
horn relay in the PDC as required.
(5) Check for continuity between the steering col-
umn half of the horn switch feed wire harness con-
nector and the horn relay control circuit cavity for
the horn relay in the PDC. There should be continu-
ity. If OK, go to Step 6. If not OK, repair the open
horn relay control circuit to the horn relay in the
PDC as required.
Fig. 3 Power Distribution Center
1 - RIGHT FENDER
2 - BATTERY
3 - POWER DISTRIBUTION CENTER
4 - COVER
8H - 6 HORNWJ
HORN RELAY (Continued)

EMIC also uses several hard wired inputs in order to
perform its many functions. The EMIC module incor-
porates a blue-green digital Vacuum Fluorescent Dis-
play (VFD) for displaying odometer and trip
odometer information.
The EMIC houses six analog gauges and has pro-
visions for up to twenty indicators (Fig. 2). The
EMIC includes the following analog gauges:
²Coolant Temperature Gauge
²Fuel Gauge
²Oil Pressure Gauge
²Speedometer
²Tachometer
²Voltage Gauge
Some of the EMIC indicators are automatically
configured when the EMIC is connected to the vehi-
cle electrical system for compatibility with certain
optional equipment or equipment required for regula-
tory purposes in certain markets. While each EMIC
may have provisions for indicators to support every
available option, the configurable indicators will not
be functional in a vehicle that does not have the
equipment that an indicator supports. The EMIC
includes provisions for the following indicators (Fig.
2):
²Airbag Indicator (with Airbags only)
²Antilock Brake System (ABS) Indicator
²Brake Indicator
²Check Gauges Indicator
²Coolant Low Indicator (with Diesel Engine
only)
²Cruise Indicator
²Four-Wheel Drive Part Time Indicator
(with Selec-Trac NVG-242 Transfer Case only)
²Front Fog Lamp Indicator (with Front Fog
Lamps only)
²High Beam Indicator
²Low Fuel Indicator
²Malfunction Indicator Lamp (MIL)
²Overdrive-Off Indicator (except Diesel
Engine)
²Rear Fog Lamp Indicator (with Rear Fog
Lamps only)
²Seatbelt Indicator
²Sentry Key Immobilizer System (SKIS)
Indicator
²Transmission Overtemp Indicator (except
Diesel Engine)²Turn Signal (Right and Left) Indicators
²Wait-To-Start Indicator (with Diesel Engine
only)
²Water-In-Fuel Indicator (with Diesel Engine
only)
Many indicators in the EMIC are illuminated by a
dedicated Light Emitting Diode (LED) that is sol-
dered onto the EMIC electronic circuit board. The
LEDs are not available for service replacement and,
if damaged or faulty, the entire EMIC must be
replaced. Base cluster illumination is accomplished
by dimmable incandescent back lighting, which illu-
minates the gauges for visibility when the exterior
lighting is turned on. Premium cluster illumination
is accomplished by a dimmable electro-luminescent
lamp that is serviced only as a unit with the EMIC.
Each of the incandescent bulbs is secured by an inte-
gral bulb holder to the electronic circuit board from
the back of the cluster housing. The incandescent
bulb/bulb holder units are available for service
replacement.
Hard wired circuitry connects the EMIC to the
electrical system of the vehicle. These hard wired cir-
cuits are integral to several wire harnesses, which
are routed throughout the vehicle and retained by
many different methods. These circuits may be con-
nected to each other, to the vehicle electrical system
and to the EMIC through the use of a combination of
soldered splices, splice block connectors, and many
different types of wire harness terminal connectors
and insulators. Refer to the appropriate wiring infor-
mation. The wiring information includes wiring dia-
grams, proper wire and connector repair procedures,
further details on wire harness routing and reten-
tion, as well as pin-out and location views for the
various wire harness connectors, splices and grounds.
The EMIC modules for this model are serviced only
as complete units. The EMIC module cannot be
adjusted or repaired. If a gauge, an LED indicator,
the VFD, the electronic circuit board, the circuit
board hardware, the cluster overlay, the electro-lumi-
nescent lamp (premium model only) or the EMIC
housing are damaged or faulty, the entire EMIC mod-
ule must be replaced. The cluster lens, hood and
mask unit and the individual incandescent lamp
bulbs with holders are available for service replace-
ment.
WJINSTRUMENT CLUSTER 8J - 3
INSTRUMENT CLUSTER (Continued)

an input from the auto headlamp light sensor to
determine the ambient light levels. If the BCM
decides that the exterior lighting is turned on in the
daylight, it overrides the selected panel dimmer
switch signal by sending a message over the PCI
data bus to illuminate all vacuum fluorescent dis-
plays at full brightness for improved visibility in day-
time light levels. The automatic parade mode has no
effect on the incandescent bulb illumination intensity.
The hard wired cluster illumination circuits
between the left (lighting) multi-function switch and
the BCM may be diagnosed using conventional diag-
nostic tools and methods. The electro-luminescent
lamp is diagnosed using the EMIC self-diagnostic
actuator test. (Refer to 8 - ELECTRICAL/INSTRU-
MENT CLUSTER - DIAGNOSIS AND TESTING).
However, proper testing of the EMIC and the elec-
tronic dimming level messages sent by the BCM over
the PCI data bus requires the use of a DRBIIItscan
tool. Refer to the appropriate diagnostic information.
CHIME SERVICE
The EMIC is programmed to request chime service
from the Body Control Module (BCM) when certain
indicators are illuminated. The EMIC chime request
for illumination of the low fuel indicator is a cus-
tomer programmable feature. When the programmed
conditions are met, the EMIC generates an electronic
chime request message and sends it over the PCI
data bus to the BCM. Upon receiving the proper
chime request, the BCM activates an integral chime
tone generator to provide the audible chime tone to
the vehicle operator. (Refer to 8 - ELECTRICAL/
CHIME WARNING SYSTEM - OPERATION). Proper
testing of the PCI data bus and the electronic chime
request message outputs from the EMIC requires the
use of a DRBIIItscan tool. Refer to the appropriate
diagnostic information.
DIAGNOSIS AND TESTING - INSTRUMENT
CLUSTER
If all of the instrument cluster gauges and/or indi-
cators are inoperative, refer to PRELIMINARY
DIAGNOSIS . If an individual gauge or Programma-
ble Communications Interface (PCI) data bus mes-
sage-controlled indicator is inoperative, refer to
ACTUATOR TEST . If an individual hard wired indi-
cator is inoperative, refer to the diagnosis and testing
information for that specific indicator. If the base
instrument cluster incandescent illumination lighting
is inoperative, refer to CLUSTER ILLUMINATION
DIAGNOSIS . If the premium instrument cluster
electro-luminescent illumination lighting is inopera-
tive, refer to ACTUATOR TEST . Refer to the appro-
priate wiring information. The wiring information
includes wiring diagrams, proper wire and connectorrepair procedures, details of wire harness routing
and retention, connector pin-out information and
location views for the various wire harness connec-
tors, splices and grounds.
NOTE: Occasionally, a condition may be encoun-
tered where the gauge pointer for the speedometer
or the tachometer becomes caught on the wrong
side of the pointer stop. To correct this condition,
the technician should use a DRBIIITscan tool and
the appropriate diagnostic information to perform
the instrument cluster self-diagnostic actuator test
procedure. When performed, the actuator test pro-
cedure will automatically return the pointer to the
correct side of the pointer stop.
PRELIMINARY DIAGNOSIS
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE SUPPLEMENTAL RESTRAINT
SYSTEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, DRIVER AIRBAG,
PASSENGER AIRBAG, SIDE CURTAIN AIRBAG,
FRONT IMPACT SENSOR, SIDE IMPACT SENSOR,
OR INSTRUMENT PANEL COMPONENT DIAGNOSIS
OR SERVICE. DISCONNECT AND ISOLATE THE
BATTERY NEGATIVE (GROUND) CABLE, THEN
WAIT TWO MINUTES FOR THE SYSTEM CAPACI-
TOR TO DISCHARGE BEFORE PERFORMING FUR-
THER DIAGNOSIS OR SERVICE. THIS IS THE ONLY
SURE WAY TO DISABLE THE SUPPLEMENTAL
RESTRAINT SYSTEM. FAILURE TO TAKE THE
PROPER PRECAUTIONS COULD RESULT IN ACCI-
DENTAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
WARNING: ON VEHICLES EQUIPPED WITH THE
PREMIUM INSTRUMENT CLUSTER, THE CLUSTER
CIRCUITRY PROVIDES AN ALTERNATING CURRENT
TO SUPPLY POWER TO THE ELECTRO-LUMINES-
CENT ILLUMINATION LAMP THROUGH A PIGTAIL
WIRE AND CONNECTOR THAT IS ACCESSIBLE AT
THE BACK OF THE CLUSTER HOUSING. USE
PROPER PRECAUTIONS WHEN HANDLING THIS
UNIT DURING DIAGNOSIS OR SERVICE TO AVOID
ELECTRICAL SHOCK AND POSSIBLE PERSONAL
INJURY.
(1) Check the fused B(+) fuse (Fuse 17 - 10
ampere) in the Junction Block (JB). If OK, go to Step
2. If not OK, repair the shorted circuit or component
as required and replace the faulty fuse.
(2) Check for battery voltage at the fused B(+) fuse
(Fuse 17 - 10 ampere) in the JB. If OK, go to Step 3.
If not OK, repair the open fused B(+) circuit between
WJINSTRUMENT CLUSTER 8J - 7
INSTRUMENT CLUSTER (Continued)

For further diagnosis of the brake indicator or the
instrument cluster circuitry that controls the indica-
tor, (Refer to 8 - ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND TESTING). The park
brake switch input to the instrument cluster can be
diagnosed using conventional diagnostic tools and
methods. For proper diagnosis of the brake fluid level
switch input to the CAB, the anti-lock brake system,
the CAB, the PCI data bus, or the electronic message
inputs to the instrument cluster that control the
brake indicator, a DRBIIItscan tool is required.
Refer to the appropriate diagnostic information.
DIAGNOSIS AND TESTING - BRAKE INDICATOR
The diagnosis found here addresses an inoperative
park brake indicator condition. If there are problems
with several indicators in the instrument cluster,
(Refer to 8 - ELECTRICAL/INSTRUMENT CLUS-
TER - DIAGNOSIS AND TESTING). If the brake
indicator stays on with the ignition switch in the On
position and the park brake released, or comes on
while driving, (Refer to 5 - BRAKES - DIAGNOSIS
AND TESTING). If no brake system problem is
found, the following procedures will help to locate a
shorted or open circuit, or a faulty park brake switch
input. Refer to the appropriate wiring information.
The wiring information includes wiring diagrams,
proper wire and connector repair procedures, details
of wire harness routing and retention, connector pin-
out information and location views for the various
wire harness connectors, splices and grounds.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE SUPPLEMENTAL RESTRAINT
SYSTEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, DRIVER AIRBAG,
PASSENGER AIRBAG, SIDE CURTAIN AIRBAG,
FRONT IMPACT SENSOR, SIDE IMPACT SENSOR,
OR INSTRUMENT PANEL COMPONENT DIAGNOSIS
OR SERVICE. DISCONNECT AND ISOLATE THE
BATTERY NEGATIVE (GROUND) CABLE, THEN
WAIT TWO MINUTES FOR THE SYSTEM CAPACI-
TOR TO DISCHARGE BEFORE PERFORMING FUR-
THER DIAGNOSIS OR SERVICE. THIS IS THE ONLY
SURE WAY TO DISABLE THE SUPPLEMENTAL
RESTRAINT SYSTEM. FAILURE TO TAKE THE
PROPER PRECAUTIONS COULD RESULT IN ACCI-
DENTAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
INDICATOR ILLUMINATES DURING BULB TEST, BUT DOES
NOT WHEN PARK BRAKE APPLIED
(1) Disconnect and isolate the battery negative
cable. Disconnect the instrument panel wire harness
connector for the park brake switch from the switch
terminal. Apply the parking brake. Check for conti-nuity between the park brake switch terminal and a
good ground. There should be continuity. If OK, go to
Step 2. If not OK, replace the faulty park brake
switch.
(2) Disconnect the instrument panel wire harness
connector for the instrument cluster from the cluster
connector receptacle. Check for continuity between
the red brake warning indicator driver circuit cavi-
ties of the instrument panel wire harness connector
for the park brake switch and the instrument panel
wire harness connector for the instrument cluster.
There should be continuity. If not OK, repair the
open red brake warning indicator driver circuit
between the park brake switch and the instrument
cluster as required.
INDICATOR REMAINS ILLUMINATED - BRAKE SYSTEM
CHECKS OK
(1) Disconnect and isolate the battery negative
cable. Disconnect the instrument panel wire harness
connector for the park brake switch from the park
brake switch terminal. Check for continuity between
the terminal of the park brake switch and a good
ground. There should be no continuity with the park
brake released, and continuity with the park brake
applied. If OK, go to Step 2. If not OK, replace the
faulty park brake switch.
(2) Disconnect the instrument panel wire harness
connector for the instrument cluster from the cluster
connector receptacle. Check for continuity between
the red brake warning indicator driver circuit cavity
of the instrument panel wire harness connector for
the park brake switch and a good ground. There
should be no continuity. If not OK, repair the shorted
red brake warning indicator driver circuit between
the park brake switch and the instrument cluster as
required.
CHECK GAUGES INDICATOR
DESCRIPTION
A check gauges indicator is standard equipment on
all instrument clusters. The check gauges indicator is
located on the right edge of the instrument cluster, to
the right of the speedometer. The check gauges indi-
cator consists of the words ªCHECK GAGESº
imprinted on a red lens. The lens is located behind a
cutout in the opaque layer of the instrument cluster
overlay. The dark outer layer of the overlay prevents
the indicator from being clearly visible when it is not
illuminated. The ªCHECK GAGESº text appears sil-
houetted against a red field through the translucent
outer layer of the overlay when the indicator is illu-
minated from behind by a Light Emitting Diode
(LED), which is soldered onto the instrument cluster
electronic circuit board. The check gauges indicator
8J - 16 INSTRUMENT CLUSTERWJ
BRAKE/PARK BRAKE INDICATOR (Continued)

switch is turned to the Off position, whichever occurs
first.
²Actuator Test- Each time the cluster is put
through the actuator test, the transmission over-tem-
perature indicator will be turned on for the duration
of the test to confirm the functionality of the bulb
and the cluster control circuitry.
The PCM or TCM continually monitors the trans-
mission temperature sensor to determine the trans-
mission operating condition. The PCM or TCM then
sends the proper trans over-temp indicator lamp-on
or lamp-off messages to the instrument cluster. If the
transmission over-temperature indicator fails to light
during the bulb test, replace the bulb with a known
good unit. If the instrument cluster turns on the
transmission over-temperature indicator due to a
high transmission oil temperature condition, it may
indicate that the transmission or the transmission
cooling system are being overloaded or that they
require service. For further diagnosis of the trans-
mission over-temperature indicator or the instrument
cluster circuitry that controls the indicator, (Refer to
8 - ELECTRICAL/INSTRUMENT CLUSTER - DIAG-
NOSIS AND TESTING). For proper diagnosis of the
transmission temperature sensor, the PCM, the
TCM, the PCI data bus, or the electronic message
inputs to the instrument cluster that control the
transmission over-temperature indicator, a DRBIIIt
scan tool is required. Refer to the appropriate diag-
nostic information.
TURN SIGNAL INDICATOR
DESCRIPTION
Two turn signal indicators, one right and one left,
are standard equipment on all instrument clusters.
The turn signal indicators are located near the upper
edge of the instrument cluster, the left one is left of
the tachometer, and the right one is right of the
speedometer. Each turn signal indicator consists of
an International Control and Display Symbol icon for
ªTurn Warningº imprinted on a green lens. Each lens
is located behind a dedicated cutout in the opaque
layer of the instrument cluster overlay. The dark
outer layer of the overlay prevents these icons from
being clearly visible when they are not illuminated.
The icons appear silhouetted against a green field
through the translucent outer layer of the overlay
when the indicator is illuminated from behind by a
replaceable incandescent bulb and bulb holder unit
located on the instrument cluster electronic circuit
board. The turn signal indicator lenses are serviced
as a unit with the instrument cluster lens, hood and
mask unit.
OPERATION
The turn signal indicators give an indication to the
vehicle operator that the turn signal (left or right
indicator flashing) or hazard warning (both left and
right indicators flashing) have been selected and are
operating. These indicators are controlled by two
individual hard wired inputs from the combination
flasher circuitry to the instrument cluster electronic
circuit board. Each turn signal indicator bulb is
grounded on the instrument cluster electronic circuit
board at all times; therefore, these indicators remain
functional regardless of the ignition switch position.
Each indicator bulb will only illuminate when it is
provided with battery current by the combination
flasher in the Junction Block (JB).
The turn signal indicators are connected in parallel
with the other turn signal circuits. This arrangement
allows the turn signal indicators to remain func-
tional, regardless of the condition of the other cir-
cuits in the turn signal and hazard warning systems.
The combination flasher outputs to the instrument
cluster turn signal indicator inputs can be diagnosed
using conventional diagnostic tools and methods. For
more information on the turn signal and hazard
warning system, (Refer to 8 - ELECTRICAL/LAMPS/
LIGHTING - EXTERIOR - OPERATION - TURN
SIGNAL & HAZARD WARNING SYSTEM).
DIAGNOSIS AND TESTING - TURN SIGNAL
INDICATOR
The diagnosis found here addresses an inoperative
turn signal indicator condition. If the problem being
diagnosed is related to inoperative turn signal or
hazard warning lamps, be certain to repair the turn
signal and hazard warning system before attempting
to diagnose or repair the turn signal indicators.
(Refer to 8 - ELECTRICAL/LAMPS/LIGHTING -
EXTERIOR - DIAGNOSIS AND TESTING - TURN
SIGNAL & HAZARD WARNING SYSTEM). If no
turn signal and hazard warning system problem is
found, the following procedure will help locate an
open in the turn signal indicator circuit. Refer to the
appropriate wiring information. The wiring informa-
tion includes wiring diagrams, proper wire and con-
nector repair procedures, details of wire harness
routing and retention, connector pin-out information
and location views for the various wire harness con-
nectors, splices and grounds.
WJINSTRUMENT CLUSTER 8J - 33
TRANS TEMP INDICATOR (Continued)

INSTALLATION - CHMSL
(1) Connect the wire harness connector.
(2) Position the CHMSL on liftgate.
(3) Install the screws attaching the CHMSL to the
liftgate.
COMBINATION FLASHER
DESCRIPTION
The combination flasher is located in the Junction
Block (JB) (Fig. 6). The JB is located underneath the
driver side of the instrument panel outboard of the
steering column. The combination flasher is a smart
relay that functions as both the turn signal system
and the hazard warning system flasher. The combi-
nation flasher contains active electronic Integrated
Circuitry (IC) elements. This flasher is designed to
handle the current flow requirements of the factory-
installed lighting. If supplemental lighting is added
to the turn signal lamp circuits, such as when towing
a trailer with lights, the combination flasher will
automatically try to compensate to keep the flash
rate the same.The combination flasher has nine blade-type termi-
nals that connect it to the vehicle electrical system.
Refer to the appropriate wiring information.
Because of the active electronic elements within
the combination flasher, it cannot be tested with con-
ventional automotive electrical test equipment. If the
combination flasher is believed to be faulty, test the
turn signal system and hazard warning system cir-
cuits.(Refer to 8 - ELECTRICAL/LAMPS/LIGHTING
- EXTERIOR - DIAGNOSIS AND TESTING - TURN
SIGNAL & HAZARD WARNING SYSTEM). The com-
bination flasher cannot be repaired or adjusted and,
if faulty or damaged, it must be replaced.
OPERATION
The combination flasher controls the following
inputs and outputs: B(+), fused ignition switch out-
put, left turn switch sense, right turn switch sense,
hazard switch sense, left front turn signal circuit,
right front turn signal circuit, left rear turn signal
circuit and right rear turn signal circuit. Constant
battery voltage is supplied to the flasher so that it
can perform the hazard warning function, and igni-
tion switched battery voltage is supplied for the turn
signal function. However, when the flasher is idle no
current is drawn through the module. The unit does
not become active until it is provided a signal ground
from the turn signal switch, hazard warning switch
or the Body Control Module (BCM).
The IC within the combination flasher (Fig. 7) con-
tains the logic that controls the flasher operation and
the flash rate. When a bulb is burnt out, or when a
circuit for a lamp is open, the turn signal flash rate
will increase. However, an open lamp circuit or burnt
out bulb does not change the hazard warning flash
rate.
Fig. 6 Combination Flasher
1 - COMBINATION FLASHER
2 - JUNCTION BLOCK
WJLAMPS/LIGHTING - EXTERIOR 8L - 7
CENTER HIGH MOUNTED STOP LAMP (Continued)