Multi function switch JEEP GRAND CHEROKEE 2003 WJ / 2.G Workshop Manual

OPERATION
The audio system components are designed to pro-
vide audio entertainment and information through
the reception, tuning and amplification of locally
broadcast radio signals in both the Amplitude Modu-
lating (AM) and Frequency Modulating (FM) com-
mercial frequency ranges. Electromagnetic radio
signals that are broadcast from a radio station
induce electrical modulations into the audio system
antenna mast. The antenna body and cable conduct
these weak signals from the antenna mast to the
radio. The radio then tunes and amplifies these weak
radio frequency signals into stronger electrical audio
signals that are required in order to operate the
audio system speakers. The speakers convert these
electrical signals into air movement, which repro-
duces the sounds being broadcast by the radio sta-
tion.
Some audio systems also offer the user the option
of selecting from and listening to prerecorded audio
cassette tapes, audio compact discs, or both. Regard-
less of the media type, the audio system components
provide the user with the ability to electronically
amplify and adjust the audio signals being repro-
duced by the speakers within the vehicle to suit the
preferences of the vehicle occupants.
The audio system components operate on battery
current received through a fuse in the Junction Block
(JB) on a fused ignition switch output (run-acc) cir-
cuit so that the system will only operate when the
ignition switch is in the On or Accessory positions.
On vehicles that are equipped with the optional
remote radio switches, the BCM receives hard wired
resistor multiplexed inputs from the remote radio
switches. The programming in the BCM allows it to
process those inputs and send the proper messages to
the radio receiver over the PCI data bus to control
the radio volume up or down, station seek up or
down, preset station advance, and mode advance
functions.On vehicles equipped with the optional memory
system, when the DDM receives a Driver 1 or Driver
2 memory recall input from the memory switch on
the driver side front door trim panel or a memory
recall message from the Remote Keyless Entry (RKE)
receiver in the PDM, the DDM sends a memory
recall message back to the radio receiver over the
PCI data bus to recall the radio station presets and
last station listened to information.
See the owner's manual in the vehicle glove box for
more information on the features, use and operation
of each of the available audio systems.
DIAGNOSIS AND TESTING - AUDIO
Any diagnosis of the Audio system should
begin with the use of the DRB IIItdiagnostic
tool. For information on the use of the DRB
IIIt, refer to the appropriate Diagnostic Service
Manual.
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: DISABLE THE AIRBAG SYSTEM
BEFORE ATTEMPTING ANY STEERING WHEEL,
STEERING COLUMN, SEAT BELT TENSIONER, SIDE
AIRBAG, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
WJAUDIO 8A - 3
AUDIO (Continued)

The two remote radio switch units share a common
steering wheel wire harness with the vehicle speed
control switches. The steering wheel wire harness is
connected to the instrument panel wire harness
through the clockspring. (Refer to 8 - ELECTRICAL/
RESTRAINTS/CLOCKSPRING - DESCRIPTION) for
more information on this component.
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.
OPERATION
The six switches in the two remote radio switch
units are normally open, resistor multiplexed
momentary switches that are hard wired to the Body
Control Module (BCM) through the clockspring. The
BCM sends a five volt reference signal to both switch
units on one circuit, and senses the status of all of
the switches by reading the voltage drop on a second
circuit.
When the BCM senses an input (voltage drop) from
any one of the remote radio switches, it sends the
proper switch status messages on the ProgrammableCommunication Interface (PCI) data bus network to
the radio receiver. The electronic circuitry within the
radio receiver is programmed to respond to these
remote radio switch status messages by adjusting the
radio settings as requested. For diagnosis of the
BCM or the PCI data bus, the use of a DRB scan tool
and the proper Diagnostic Procedures manual are
recommended.
For more information on the features and control
functions for each of the remote radio switches, see
the owner's manual in the vehicle glove box.
DIAGNOSIS AND TESTING - REMOTE
SWITCHES
Any diagnosis of the Audio system should
begin with the use of the DRB IIItdiagnostic
tool. For information on the use of the DRB
IIIt, refer to the appropriate Diagnostic Service
Manual.
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: DISABLE THE AIRBAG SYSTEM
BEFORE ATTEMPTING ANY STEERING WHEEL,
STEERING COLUMN, SEAT BELT TENSIONER, SIDE
AIRBAG, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Disconnect and isolate the battery negative
cable. Remove the remote radio switch(es) (Fig. 16)
from the steering wheel.
(2) Use an ohmmeter to check the switch resis-
tances as shown in the Remote Radio Switch Test
chart. If the remote radio switch resistances check
OK, go to Step 3. If not OK, replace the faulty
switch.
Fig. 15 Remote Radio Switches
1 - PRESET ADVANCE
2 - SEEK
3 - MODE ADVANCE
4 - VOLUME
8A - 20 AUDIOWJ
REMOTE SWITCHES (Continued)

CHIME WARNING SYSTEM DIAGNOSIS
CONDITION POSSIBLE CAUSES CORRECTION
NO KEY-IN IGNITION OR
HEADLAMPS-ON WARNING
CHIME WITH DRIVER SIDE
FRONT DOOR OPEN1. Faulty door ajar switch or
circuits.1. Check that interior lights illuminate with driver
door open. If not OK, repair the interior lighting
system as required.
2. Faulty headlamp switch
(left multi-function switch) or
circuits.2. Check for proper exterior lighting operation. If
not OK, repair the exterior lighting system as
required.
3. Key-in ignition switch
sense circuit open.2. Check for continuity between the key-in ignition
switch sense circuit of the instrument panel wire
harness connector for the ignition switch and the
body wire harness connector for the junction
block. Repair the key-in ignition switch sense
circuit, if required.
4. Faulty ignition switch. 3. Check for continuity between the two terminals
in the ignition switch connector. There should be
continuity with a key in the ignition lock cylinder.
Replace the faulty ignition switch, if required.
CHIME SOUNDS WITH
DRIVER SIDE FRONT
DOOR OPEN1. Key-in ignition switch
sense circuit shorted.1. Disconnect the instrument panel wire harness
connector for the ignition switch and the body
wire harness connector for the junction block.
There should be no continuity between the key-in
ignition switch sense circuit of the instrument
panel wire harness connector for the ignition
switch and a good ground. Repair the key-in
ignition switch sense circuit, if required.
2. Faulty ignition switch. 2. Check for continuity between the two terminals
in the ignition switch connector. There should be
no continuity with the key removed from the
ignition lock cylinder. Replace the faulty ignition
switch, if required.
NO CHIMES AT ALL TIMES 1. Faulty Body Control
Module (BCM).1. Use a DRBIIITscan tool and refer to the
appropriate diagnostic information. Replace the
faulty BCM, if required
8B - 4 CHIME/BUZZERWJ
CHIME WARNING SYSTEM (Continued)

(5) Connect the two instrument panel wire harness
connectors to the BCM.
(6) Reinstall the instrument panel fuse cover to
the bottom of the BCM and JB unit. (Refer to 8 -
ELECTRICAL/POWER DISTRIBUTION/FUSE
COVER - INSTALLATION).
(7) Connect the battery negative cable.
COMMUNICATION
DESCRIPTION
The Programmable Communication Interface (PCI)
data bus system is a single wire multiplex system
used for vehicle communications. Multiplexing is a
system that enables the transmission of several mes-
sages over a single channel or circuit.
Many of the control modules in a vehicle require
information from the same sensing device. Multiplex-
ing reduces wire harness complexity, sensor current
loads and controller hardware because each sensing
device is connected to only one controller, which
reads and distributes the sensor information to the
other controllers over the data bus. Also, because
each controller on the data bus can access the con-
troller sensor inputs to every other controller on the
data bus, more function and feature capabilities are
possible.
A multiplex system allows the information flowing
between controllers to be monitored using a diagnos-
tic scan tool. This system allows a control module to
broadcast message data out onto the bus where all
other control modules can read the messages that are
being sent. When a module reads a message on the
data bus that it requires, it relays that message to
its microprocessor. Each module ignores the mes-
sages on the data bus that it dosen't recognize.
OPERATION
Data exchange between modules is achieved by
serial transmission of encoded data over a single wire
broadcast network. The PCI data bus messages are
carried over the bus in the form of Variable Pulse
Width Modulated (VPWM) signals. The PCI data bus
speed is an average 10.4 Kilo-bits per second (Kbps).
The voltage network used to transmit messages
requires biasing and termination. Each module on
the PCI data bus system provides its own biasing
and termination. Each module (also referred to as a
node) terminates the bus through a terminating
resistor and a terminating capacitor. The Powertrain
Control Module (PCM) is the only dominant node for
the PCI data bus system.
The PCI bus uses low and high voltage levels to
generate signals. The voltage on the buss varies
between zero and seven and one-half volts. The lowand high voltage levels are generated by means of
variable-pulse width modulation to form signals of
varying length.
When a module is transmitting on the bus, it is
reading the bus at the same time to ensure message
integrity.
Each module is capable of transmitting and receiv-
ing data simultaneously.
The PCI data bus can be monitored using the
DRBIIItscan tool. It is possible for the bus to pass
all DRBIIIttests and still be faulty if the voltage
parameters are all within the specified range and
false messages are being sent.
CONTROLLER ANTILOCK
BRAKE
DESCRIPTION
The Controler Antilock Brake (CAB) is mounted to
the Hydraulic Control Unit (HCU) and operates the
ABS system (Fig. 4).
OPERATION
The CAB voltage is supplied by the ignition switch
in the RUN position. The CAB contains dual micro-
processors. A logic block in each microprocessor
receives identical sensor signals. These signals are
processed and compared simultaneously. The CAB
contains a self check program that illuminates the
ABS warning light when a system fault is detected.
Faults are stored in a diagnostic program memory
and are accessible with the DRBIIItscan tool. ABS
faults remain in memory until cleared, or until after
the vehicle is started approximately 50 times. Stored
Fig. 4 Controller Antilock Brakes
1 - HCU
2 - MOTOR
3 - CAB
8E - 6 ELECTRONIC CONTROL MODULESWJ
BODY CONTROL MODULE (Continued)

STANDARD PROCEDURE - IGNITION-OFF
DRAW TEST
The term Ignition-Off Draw (IOD) identifies a nor-
mal condition where power is being drained from the
battery with the ignition switch in the Off position. A
normal vehicle electrical system will draw from five
to thirty-five milliamperes (0.005 to 0.035 ampere)
with the ignition switch in the Off position, and all
non-ignition controlled circuits in proper working
order. Up to thirty-five milliamperes are needed to
enable the memory functions for the Powertrain Con-
trol Module (PCM), digital clock, electronically tuned
radio, and other modules which may vary with the
vehicle equipment.
A vehicle that has not been operated for approxi-
mately twenty days, may discharge the battery to an
inadequate level. When a vehicle will not be used for
twenty days or more (stored), remove the IOD fuse
from the Power Distribution Center (PDC). This will
reduce battery discharging.Excessive IOD can be caused by:
²Electrical items left on.
²Faulty or improperly adjusted switches.
²Faulty or shorted electronic modules and compo-
nents.
²An internally shorted generator.
²Intermittent shorts in the wiring.
If the IOD is over thirty-five milliamperes, the
problem must be found and corrected before replac-
ing a battery. In most cases, the battery can be
charged and returned to service after the excessive
IOD condition has been corrected.
(1) Verify that all electrical accessories are off.
Turn off all lamps, remove the ignition key, and close
all doors. If the vehicle is equipped with an illumi-
nated entry system or an electronically tuned radio,
allow the electronic timer function of these systems
to automatically shut off (time out). This may take
up to three minutes. See the Electronic Module Igni-
tion-Off Draw Table for more information.
ELECTRONIC MODULE IGNITION-OFF DRAW (IOD) TABLE
ModuleTime Out?
(If Yes, Interval And Wake-Up Input)IODIOD After Time
Out
Radio No1to3
milliamperesN/A
Audio Power
AmplifierNoup to 1
milliampereN/A
Body Control Module
(BCM)No5.90
milliamperes
(max.)N/A
Powertrain Control
Module (PCM)No 0.95 milliampere N/A
Transmission Control
Module (TCM) 4.7L
w/45RFEYES (20 minutes, ignition on) 130 milliamperes 0.64 milliampere
ElectroMechanical
Instrument Cluster
(EMIC)No 0.44 milliampere N/A
Combination Flasher No 0.08 milliampere N/A
(2) Determine that the underhood lamp is operat-
ing properly, then disconnect the lamp wire harness
connector or remove the lamp bulb.
(3) Disconnect the battery negative cable.
(4) Set an electronic digital multi-meter to its
highest amperage scale. Connect the multi-meter
between the disconnected battery negative cable ter-
minal clamp and the battery negative terminal post.
Make sure that the doors remain closed so that the
illuminated entry system is not activated. The multi-
meter amperage reading may remain high for up tothree minutes, or may not give any reading at all
while set in the highest amperage scale, depending
upon the electrical equipment in the vehicle. The
multi-meter leads must be securely clamped to the
battery negative cable terminal clamp and the bat-
tery negative terminal post. If continuity between the
battery negative terminal post and the negative cable
terminal clamp is lost during any part of the IOD
test, the electronic timer function will be activated
and all of the tests will have to be repeated.
WJBATTERY SYSTEM 8F - 13
BATTERY (Continued)

certain conditions or inputs to provide the vehicle
operator with an audible alert to supplement a visual
indication.
The EMIC circuitry operates on battery current
received through fused B(+) fuses in the Power Dis-
tribution Center (PDC) and the Junction Block (JB)
on a non-switched fused B(+) circuit, and on battery
current received through a fused ignition switch out-
put (run-start) fuse in the JB on a fused ignition
switch output (run-start) circuit. This arrangement
allows the EMIC to provide some features regardless
of the ignition switch position, while other features
will operate only with the ignition switch in the On
or Start positions. The EMIC circuitry is grounded
through two separate ground circuits of the instru-
ment panel wire harness. These ground circuits
receive ground through take outs of the instrument
panel wire harness with eyelet terminal connectors
that are secured by a nut to a ground stud located on
the floor panel transmission tunnel beneath the cen-
ter floor console, just forward of the Airbag Control
Module (ACM).
The EMIC also has a self-diagnostic actuator test
capability, which will test each of the PCI bus mes-
sage-controlled functions of the cluster by lighting
the appropriate indicators (except the airbag indica-
tor), sweeping the gauge needles across the gauge
faces from their minimum to their maximum read-
ings, and stepping the odometer display sequentially
from all zeros through all nines. (Refer to 8 - ELEC-
TRICAL/INSTRUMENT CLUSTER - DIAGNOSIS
AND TESTING). The self-diagnostic actuator test
can be initialized manually or using a DRBIIItscan
tool. Refer to the appropriate diagnostic information.
See the owner's manual in the vehicle glove box for
more information on the features, use and operation
of the EMIC.
GAUGES
All gauges receive battery current through the
EMIC circuitry when the ignition switch is in the On
or Start positions. With the ignition switch in the Off
position battery current is not supplied to any
gauges, and the EMIC circuitry is programmed to
move all of the gauge needles back to the low end of
their respective scales. Therefore, the gauges do not
accurately indicate any vehicle condition unless the
ignition switch is in the On or Start positions. All of
the EMIC gauges, except the odometer, are air core
magnetic units. Two fixed electromagnetic coils are
located within each gauge. These coils are wrapped
at right angles to each other around a movable per-
manent magnet. The movable magnet is suspended
within the coils on one end of a pivot shaft, while the
gauge needle is attached to the other end of the
shaft. One of the coils has a fixed current flowingthrough it to maintain a constant magnetic field
strength. Current flow through the second coil
changes, which causes changes in its magnetic field
strength. The current flowing through the second coil
is changed by the EMIC circuitry in response to mes-
sages received over the PCI data bus. The gauge nee-
dle moves as the movable permanent magnet aligns
itself to the changing magnetic fields created around
it by the electromagnets.
The gauges are diagnosed using the EMIC self-di-
agnostic actuator test. (Refer to 8 - ELECTRICAL/
INSTRUMENT CLUSTER - DIAGNOSIS AND
TESTING). Proper testing of the PCI data bus, and
the data bus message inputs to the EMIC that con-
trol each gauge requires the use of a DRBIIItscan
tool. Refer to the appropriate diagnostic information.
Specific operation details for each gauge may be
found elsewhere in this service information.
VACUUM-FLUORESCENT DISPLAY
The Vacuum-Fluorescent Display (VFD) module is
soldered to the EMIC circuit board. The display is
active with the ignition switch in the On or Start
positions, and inactive when the ignition switch is in
any other position. The illumination intensity of the
VFD is controlled by the EMIC circuitry based upon
electronic dimming level messages received from the
BCM over the PCI data bus, and is synchronized
with the illumination intensity of other VFDs in the
vehicle. The BCM provides dimming level messages
based upon internal programming and inputs it
receives from the control knob and control ring on
the control stalk of the left (lighting) multi-function
switch on the steering column.
The VFD has several display capabilities including
odometer and trip odometer information. An odome-
ter/trip odometer switch on the EMIC circuit board is
used to control the display modes. This switch is
actuated manually by depressing the odometer/trip
odometer switch button that extends through the
lower edge of the cluster lens, just right of the speed-
ometer. Actuating this switch momentarily with the
ignition switch in the On position will toggle the
VFD between the odometer and trip odometer modes.
The EMIC microprocessor remembers which display
mode is active when the ignition switch is turned to
the Off position, and returns the display to that
mode when the ignition switch is turned On again.
Depressing the switch button for about two seconds
while the VFD is in the trip odometer mode will
reset the trip odometer value to zero. Holding this
switch depressed while turning the ignition switch
from the Off position to the On position will initiate
the EMIC self-diagnostic actuator test. Refer to the
appropriate diagnostic information for additional
details on this VFD function.
WJINSTRUMENT CLUSTER 8J - 5
INSTRUMENT CLUSTER (Continued)

The VFD is diagnosed using the EMIC self-diag-
nostic actuator test. (Refer to 8 - ELECTRICAL/IN-
STRUMENT CLUSTER - DIAGNOSIS AND
TESTING). Proper testing of the PCI data bus and
the data bus message inputs to the EMIC that con-
trol the VFD functions requires the use of a DRBIIIt
scan tool. Refer to the appropriate diagnostic infor-
mation. Specific operation details for the odometer
and trip odometer functions of the VFD may be found
elsewhere in this service information.
INDICATORS
Indicators are located in various positions within
the EMIC and are all connected to the EMIC circuit
board. The turn signal indicators are hard wired. The
brake indicator is controlled by PCI data bus mes-
sages from the Controller Antilock Brake (CAB) as
well as by hard wired park brake switch and brake
fluid level switch inputs to the EMIC. The Malfunc-
tion Indicator Lamp (MIL) is normally controlled by
PCI data bus messages from the Powertrain Control
Module (PCM); however, if the EMIC loses PCI data
bus communication, the EMIC circuitry will automat-
ically turn the MIL on until PCI data bus communi-
cation is restored. The EMIC uses PCI data bus
messages from the Airbag Control Module (ACM), the
BCM, the PCM, the CAB, the Sentry Key Immobi-
lizer Module (SKIM), and the Transmission Control
Module (TCM) to control all of the remaining indica-
tors.
The various indicators are controlled by different
strategies; some receive fused ignition switch output
from the EMIC circuitry and have a switched ground,
others are grounded through the EMIC circuitry and
have a switched battery feed, while still others are
completely controlled by the EMIC microprocessor
based upon various hard wired and electronic mes-
sage inputs. Some indicators are illuminated at a
fixed intensity, while the illumination intensity of
others is synchronized with that of the EMIC general
illumination lamps.
The hard wired indicators are diagnosed using con-
ventional diagnostic methods. The EMIC and PCI
bus message controlled indicators are diagnosed
using the EMIC self-diagnostic actuator test. (Refer
to 8 - ELECTRICAL/INSTRUMENT CLUSTER -
DIAGNOSIS AND TESTING). Proper testing of the
PCI data bus and the electronic data bus message
inputs to the EMIC that control each indicator
require the use of a DRBIIItscan tool. Refer to the
appropriate diagnostic information. Specific details of
the operation for each indicator may be found else-
where in this service information.CLUSTER ILLUMINATION
Two types of general cluster illumination are avail-
able in this model. Base versions of the EMIC have
several incandescent illumination lamps, while pre-
mium versions of the EMIC have a single electro-lu-
minescent lamp. Both types of lamps provide cluster
back lighting whenever the exterior lighting is
turned On with the control knob on the left (lighting)
multi-function switch control stalk. The illumination
intensity of these lamps is adjusted by the EMIC
microprocessor based upon electronic dimming level
messages received from the Body Control Module
(BCM) over the PCI data bus. The BCM provides
electronic dimming level messages to the EMIC
based upon internal programming and inputs it
receives when the control ring on the left (lighting)
multi-function switch control stalk is rotated (down
to dim, up to brighten) to one of six available minor
detent positions.
The incandescent illumination lamps receive bat-
tery current at all times, while the ground for these
lamps is controlled by a 12-volt Pulse Width Modu-
lated (PWM) output of the EMIC electronic circuitry.
The illumination intensity of these bulbs and of the
vacuum-fluorescent electronic display are controlled
by the instrument cluster microprocessor based upon
dimming level messages received from the Body Con-
trol Module (BCM) over the PCI data bus. The BCM
uses inputs from the headlamp and panel dimmer
switches within the left (lighting) multi-function
switch control stalk and internal programming to
decide what dimming level message is required. The
BCM then sends the proper dimming level messages
to the EMIC over the PCI data bus.
The electro-luminescent lamp unit consists of lay-
ers of phosphor, carbon, idium tin oxide, and dielec-
tric applied by a silk-screen process between two
polyester membranes and includes a short pigtail
wire and connector. The lamp pigtail wire is con-
nected to a small connector receptacle on the EMIC
circuit board through a small clearance hole in the
cluster housing rear cover. The EMIC electronic cir-
cuitry also uses a PWM strategy to control the illu-
mination intensity of this lamp; however, the EMIC
powers this lamp with an Alternating Current (AC)
rated at 80 volts rms (root mean squared) and 415
Hertz, which excites the phosphor particles causing
them to luminesce.
The BCM also has several hard wired panel lamp
driver outputs and sends the proper panel lamps
dimming level messages over the PCI data bus to
coordinate the illumination intensity of all of the
instrument panel lighting and the VFDs of other
electronic modules on the PCI data bus. Vehicles
equipped with the Auto Headlamps option have an
automatic parade mode. In this mode, the BCM uses
8J - 6 INSTRUMENT CLUSTERWJ
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)

exterior lighting is turned On, the illumination inten-
sity of the coolant low indicator is dimmable, which
is adjusted using the panel lamps dimmer control
ring on the control stalk of the left multi-function
switch. The coolant low indicator lens is serviced as a
unit with the instrument cluster lens, hood and mask
unit.
OPERATION
The coolant low indicator gives an indication to the
vehicle operator when the diesel engine coolant level
is low. This indicator is controlled by a transistor on
the instrument cluster circuit board based upon clus-
ter programming and electronic messages received by
the cluster from the Body Control Module (BCM)
over the Programmable Communications Interface
(PCI) data bus. The coolant low indicator bulb is
completely controlled by the instrument cluster logic
circuit, and that logic will only allow this indicator to
operate when the instrument cluster receives a bat-
tery current input on the fused ignition switch out-
put (run-start) circuit. Therefore, the indicator will
always be off when the ignition switch is in any posi-
tion except On or Start. The bulb only illuminates
when it is provided a path to ground by the instru-
ment cluster transistor. The instrument cluster will
turn on the coolant low indicator for the following
reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the coolant low indicator is
illuminated for about three seconds as a bulb test.
²Coolant Low Indicator Lamp-On Message-
Each time the cluster receives a coolant low indicator
lamp-on message from the BCM indicating the
engine coolant is below the minimum level in the
coolant reservoir, the coolant low indicator will be
illuminated. The indicator remains illuminated until
the cluster receives a coolant low indicator lamp-off
message from the BCM indicating that the engine
coolant level is above the minimum level.
²Actuator Test- Each time the cluster is put
through the actuator test, the coolant low indicator
will be turned on for the duration of the test to con-
firm the functionality of the bulb and the cluster con-
trol circuitry.
The BCM continually monitors the input from the
coolant level switch, then sends the proper coolant
low indicator lamp-on and lamp-off messages to the
instrument cluster. If the coolant low indicator fails
to light during the bulb test, replace the bulb with a
known good unit. For further diagnosis of the coolant
low indicator or the instrument cluster circuitry that
controls the indicator, (Refer to 8 - ELECTRICAL/IN-
STRUMENT CLUSTER - DIAGNOSIS AND TEST-
ING). For proper diagnosis of the coolant level
switch, the BCM, the PCI data bus, or the electronicmessage inputs to the instrument cluster that control
the coolant low indicator, a DRBIIItscan tool is
required. Refer to the appropriate diagnostic infor-
mation.
CRUISE INDICATOR
DESCRIPTION
A cruise indicator is standard equipment on all
instrument clusters, but is only functional on vehi-
cles equipped with the optional speed control system.
The cruise indicator is located on the right edge of
the instrument cluster, to the right of the speedome-
ter. The cruise indicator consists of the word
ªCRUISEº imprinted on a blue/green 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 ªCRUISEº text
appears silhouetted against a blue/green field
through the translucent outer layer of the overlay
when the indicator is illuminated from behind by a
replaceable bulb and bulb holder unit located on the
instrument cluster electronic circuit board. When the
exterior lighting is turned On, the illumination inten-
sity of the cruise indicator is dimmable, which is
adjusted using the panel lamps dimmer control ring
on the control stalk of the left multi-function switch.
The cruise indicator lens is serviced as a unit with
the instrument cluster lens, hood and mask unit.
OPERATION
The cruise indicator gives an indication to the vehi-
cle operator when the speed control system is turned
On, regardless of whether the speed control is
engaged. This indicator is controlled by a transistor
on the instrument cluster electronic circuit board
based upon cluster programming and electronic mes-
sages received by the cluster from the Powertrain
Control Module (PCM) over the Programmable Com-
munications Interface (PCI) data bus. The cruise
indicator bulb is completely controlled by the instru-
ment cluster logic circuit, and that logic will only
allow this indicator to operate when the instrument
cluster receives a battery current input on the fused
ignition switch output (run-start) circuit. Therefore,
the indicator will always be off when the ignition
switch is in any position except On or Start. The bulb
only illuminates when it is provided a path to ground
by the instrument cluster transistor. The instrument
cluster will turn on the cruise indicator for the fol-
lowing reasons:
²Cruise Indicator Lamp-On Message- Each
time the cluster receives a cruise indicator lamp-on
message from the PCM indicating the speed control
8J - 18 INSTRUMENT CLUSTERWJ
COOLANT LOW INDICATOR (Continued)

the gauge needle at the last indication for about
twelve seconds or until a new engine temperature
message is received, whichever occurs first. After
twelve seconds, the cluster will return the gauge nee-
dle to the low end of the gauge scale.
²Actuator Test- Each time the cluster is put
through the actuator test, the gauge needle will be
swept across the entire gauge scale and back in order
to confirm the functionality of the gauge and the
cluster control circuitry.
The PCM continually monitors the engine coolant
temperature sensor to determine the engine operat-
ing temperature. The PCM then sends the proper
engine coolant temperature messages to the instru-
ment cluster. For further diagnosis of the engine cool-
ant temperature gauge or the instrument cluster
circuitry that controls the gauge, (Refer to 8 - ELEC-
TRICAL/INSTRUMENT CLUSTER - DIAGNOSIS
AND TESTING). If the instrument cluster moves the
engine coolant temperature gauge needle to indicate
a high or critical engine temperature, it may indicate
that the engine or the engine cooling system requires
service. For proper diagnosis of the engine coolant
temperature sensor, the PCM, the PCI data bus, or
the electronic message inputs to the instrument clus-
ter that control the engine coolant temperature
gauge, a DRBIIItscan tool is required. Refer to the
appropriate diagnostic information.
FRONT FOG LAMP INDICATOR
DESCRIPTION
A front fog lamp indicator is standard equipment
on all instrument clusters, but is only functional on
vehicles equipped with the optional front fog lamps.
The front fog lamp indicator is located on the left
edge of the instrument cluster, to the left of the
tachometer. The front fog lamp indicator consists of
an International Control and Display Symbol icon for
ªFront Fog Lightº imprinted on a green 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 icon
appears silhouetted against a green field through the
translucent outer layer of the overlay when the indi-
cator is illuminated from behind by a replaceable
incandescent bulb and bulb holder unit located on
the instrument cluster electronic circuit board. When
the exterior lighting is turned On, the illumination
intensity of the front fog lamp indicator is dimmable,
which is adjusted using the panel lamps dimmer con-
trol ring on the control stalk of the left multi-func-
tion switch. The front fog lamp indicator lens isserviced as a unit with the instrument cluster lens,
hood and mask unit.
OPERATION
The front fog lamp indicator gives an indication to
the vehicle operator whenever the front fog lamps
are illuminated. This indicator is controlled by a
transistor on the instrument cluster circuit board
based upon cluster programming and electronic mes-
sages received by the cluster from the Body Control
Module (BCM) over the Programmable Communica-
tions Interface (PCI) data bus. The front fog lamp
indicator bulb is completely controlled by the instru-
ment cluster logic circuit, and that logic will allow
this indicator to operate whenever the instrument
cluster receives a battery current input on the fused
B(+) circuit. Therefore, the indicator can be illumi-
nated regardless of the ignition switch position. The
bulb only illuminates when it is provided a path to
ground by the instrument cluster transistor. The
instrument cluster will turn on the front fog lamp
indicator for the following reasons:
²Front Fog Lamp Indicator Lamp-On Mes-
sage- Each time the cluster receives a front fog
lamp indicator lamp-on message from the BCM indi-
cating that the front fog lamps are turned On, the
front fog lamp indicator will be illuminated. The indi-
cator remains illuminated until the cluster receives a
front fog lamp indicator lamp-off message from the
BCM.
²Actuator Test- Each time the cluster is put
through the actuator test, the front fog lamp indica-
tor will be turned on for the duration of the test to
confirm the functionality of the bulb and the cluster
control circuitry.
The BCM continually monitors the exterior light-
ing (left multi-function) switch to determine the
proper outputs to the front fog lamp relay. The BCM
then sends the proper front fog lamp indicator
lamp-on and lamp-off messages to the instrument
cluster. If the front fog lamp indicator fails to light
during the actuator test, replace the bulb with a
known good unit. For further diagnosis of the front
fog lamp indicator or the instrument cluster circuitry
that controls the indicator, (Refer to 8 - ELECTRI-
CAL/INSTRUMENT CLUSTER - DIAGNOSIS AND
TESTING). For proper diagnosis of the front fog
lamp system, the BCM, the PCI data bus, or the elec-
tronic message inputs to the instrument cluster that
control the front fog lamp indicator, a DRBIIItscan
tool is required. Refer to the appropriate diagnostic
information.
8J - 20 INSTRUMENT CLUSTERWJ
ENGINE TEMPERATURE GAUGE (Continued)