2003 JEEP GRAND CHEROKEE BCM wiring

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)

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)

CONDITION POSSIBLE CAUSES CORRECTION
3. Faulty headlamp switch. 3. Refer to BCM diagnostics.
4. Blown fuse for headlamps. 4. Replace fuse refer to Electrical, Wiring
Information.
5. Broken connector terminal or wire
splice in headlamp circuit.5. Repair connector terminal or wire splice.
6. Both headlamp bulbs defective. 6. Replace both headlamp bulbs.
*Canada vehicles must have lamps ON.
FOG LAMP
CONDITION POSSIBLE CAUSES CORRECTION
FOG LAMPS ARE DIM
WITH ENGINE IDLING
OR IGNITION TURNED
OFF.1. Loose or corroded battery cables. 1. Clean and secure battery cable clamps
and posts.
2. Loose or worn generator drive belt. 2. Adjust or replace generator drive belt.
3. Charging system output too low. 3. Test and repair charging system. Refer to
Electrical, Charging,
4. Battery has insufficient charge. 4. Test battery state-of -charge. Refer to
Electrical, Battery System.
5. Battery is sulfated or shorted. 5. Load test battery. Refer to Electrical,
Battery System.
6. Poor lighting circuit Z1-ground. 6. Test for voltage drop across Z1-ground
locations. Refer to Electrical, Wiring
Information.
FOG LAMP BULBS BURN
OUT FREQUENTLY1. Charging system output too high. 1. Test and repair charging system. Refer to
Electrical, Charging.
2. Loose or corroded terminals or
splices in circuit.2. Inspect and repair all connectors and
splices. Refer to Electrical, Wiring
Information.
FOG LAMPS ARE DIM
WITH ENGINE RUNNING
ABOVE IDLE1. Charging system output too low. 1. Test and repair charging system. Refer to
Electrical, Charging.
2. Poor lighting circuit Z1-ground. 2. Test for voltage drop across Z1-ground
locations. Refer to Electrical, Wiring
Information.
3. High resistance in fog lamp circuit. 3. Test amperage draw of fog lamp circuit.
FOG LAMPS FLASH
RANDOMLY1. Poor lighting circuit Z1-ground. 1. Test for voltage drop across Z1-ground
locations. Refer to Electrical, Wiring
Information.
2. High resistance in fog lamp circuit. 2. Test amperage draw of fog lamp circuit.
3. Faulty multifunction switch. 3. Refer to Electrical, Electronic Control
Modules.
4. Loose or corroded terminals or
splices in circuit.4. Inspect and repair all connectors and
splices. Refer to Electrical, Wiring
Information.
WJLAMPS/LIGHTING - EXTERIOR 8L - 13
HEADLAMP (Continued)

INSTALLATION - BULB
CAUTION: Do not touch the bulb glass with fingers
or other oily surfaces. Reduced bulb life will result.
(1) Position the bulb into socket and push into
place.
(2) Position the bulb socket in headlamp and turn
the bulb socket one quarter turn clockwise.
(3) Install the headlamp.
HEADLAMP SWITCH
DESCRIPTION
The headlamp switch is part of the left multi-func-
tion switch. A knob on the end of the multi-function
switch control stalk controls all of the exterior light-
ing switch functions. The exterior lighting switch is
hard wired to the Body Control Module (BCM).
The exterior lighting switch cannot be adjusted or
repaired and, if faulty or damaged, the entire left
multi-function switch unit must be replaced. (Refer
to 8 - ELECTRICAL/LAMPS/LIGHTING - EXTERI-
OR/TURN SIGNAL/HAZARD SWITCH - REMOVAL)
for the service procedures. (Refer to 8 - ELECTRI-
CAL/ELECTRONIC CONTROL MODULES/BODY
CONTROL/CENTRAL TIMER MODUL - DESCRIP-
TION) for more information on this component.
OPERATION
The exterior lighting switch uses a hard wired five
volt reference circuit from the BCM, resistor multi-
plexing and a hard wired switch output circuit to
provide the BCM with a zero to five volt signal thatindicates the status of all of the exterior lighting
switch settings. The BCM then uses control outputs
to energize the headlamp and park lamp relays that
activate the exterior lighting circuits.
The BCM monitors the exterior lighting switch sta-
tus, then sends the proper switch status messages to
other modules over the Programmable Communica-
tions Interface (PCI) data bus network. The exterior
lighting switch status is also used by the BCM as an
input for chime warning system operation.
DIAGNOSIS AND TESTING Ð HEADLAMP
SWITCH
Before testing the headlamp switch, turn on the
exterior lighting and open the driver side front door.
If the exterior lamps of the vehicle operate, but there
is no chime warning issued with the driver side front
door open, (Refer to 8 - ELECTRICAL/LAMPS/
LIGHTING - INTERIOR/DOOR AJAR SWITCH -
DIAGNOSIS AND TESTING). If the exterior lamps
of the vehicle are inoperative, but the chime warning
is issued, (Refer to 8 - ELECTRICAL/LAMPS/LIGHT-
ING - EXTERIOR - DIAGNOSIS AND TESTING).
If the exterior lamps and the chime warning are
both inoperative, test the left multi-function switch.
(Refer to 8 - ELECTRICAL/LAMPS/LIGHTING -
EXTERIOR - DIAGNOSIS AND TESTING). If the
multi-function switch tests OK, proceed as follows.
The following tests will help to locate a short or open
in the hard wired circuits between the multi-function
switch and the Body Control Module (BCM). For
complete circuit diagrams, refer to the appropriate
wiring information.
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. Disconnect the instrument panel wire harness
connector from the left multi-function switch connec-
tor. Disconnect the instrument panel wire harness
connector from the Body Control Module (BCM).
Check for continuity between the headlamp switch
mux circuit of the instrument panel wire harness
connector for the multi-function switch and a good
ground. There should be no continuity. If OK, go to
Step 2. If not OK, repair the shorted headlamp
switch mux circuit.
(2) Check for continuity between the headlamp
switch mux circuit of the instrument panel wire har-
Fig. 13 Headlamp Bulb
1 - HIGH BEAM BULB
2 - LOW BEAM BULB
3 - MARKER BULB
4 - PARK/TURN SIGNAL BULB
WJLAMPS/LIGHTING - EXTERIOR 8L - 15
HEADLAMP (Continued)

²Hazard Warning Control- The hazard warn-
ing push button is pressed down to activate the haz-
ard warning system, and pressed down again to turn
the system off. The left multi-function switch pro-
vides a ground to the hazard warning sense input of
the combination flasher to control activation of the
hazard warning lamps.
²Headlamps- The Body Control Module (BCM)
monitors the left multi-function switch then, based
upon that multiplexed input, controls an output to
the headlamp low or high beam relays to illuminate
or extinguish the headlamps.
²Headlamp Beam Selection- The Body Control
Module (BCM) monitors the left multi-function
switch then, based upon that switched ground input,
controls an output to the headlamp low or high beam
relays to activate the selected headlamp beam.
²Headlamp Optical Horn- The Body Control
Module (BCM) monitors the left multi-function
switch then, based upon that switched ground input,
controls an output to the headlamp high beam relay
to activate the headlamp high beams.
²Park Lamps- The Body Control Module (BCM)
monitors the left multi-function switch then, based
upon that multiplexed input, controls an output to
the park lamp relay to illuminate or extinguish the
parking lamps.
²Rear Fog Lamps- The Body Control Module
(BCM) monitors the left multi-function switch then,
based upon that multiplexed input, controls an out-
put to the rear fog lamp relay to illuminate or extin-
guish the rear fog lamps.
²Turn Signal Control- The left multi-function
switch control stalk actuates the turn signal switch.
The Body Control Module (BCM) monitors the left
multi-function switch then, based upon that multi-
plexed input, provides a variable voltage output to
control the lighting of the turn signals.
Following are descriptions of the how the left
multi-function switch operates to control the many
interior lighting functions and features it provides:
²Panel Lamps Dimming- The Body Control
Module (BCM) monitors the left multi-function
switch then, based upon that multiplexed input, pro-
vides a variable voltage output through several panel
lamps driver circuits to control the lighting of many
incandescent panel lamps. The BCM also sends panel
lamps dimming messages over the Programmable
Communications Interface (PCI) data bus to other
modules to control Display lighting levels in those
modules.²Interior Lamps Defeat- The Body Control
Module (BCM) monitors the left multi-function
switch then, based upon that multiplexed input,
internally disables the function the BCM normally
provides to control the illumination of the interior
lamps.
²Interior Lamps On- The Body Control Module
(BCM) monitors the left multi-function switch then,
based upon that multiplexed input, provides a control
output to activate all of the interior lamp circuits.
²Parade Mode- The Body Control Module
(BCM) monitors the left multi-function switch then,
based upon that multiplexed input, provides a volt-
age output through several panel lamps driver cir-
cuits to control the lighting of many incandescent
panel lamps. The BCM also sends panel lamps dim-
ming messages over the Programmable Communica-
tions Interface (PCI) data bus to other modules on
the bus to control lighting levels in those modules.
DIAGNOSIS AND TESTING - LEFT MULTI -
FUNCTION SWITCH
Refer to the appropriate wiring information.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, 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. Disconnect the instrument panel wire harness
connector from the multi-function switch connector.
(2) Using an ohmmeter, perform the continuity
and resistance tests at the terminals in the multi-
function switch connector as shown in the Left Multi-
Function Switch Test chart (Fig. 23).
8L - 20 LAMPS/LIGHTING - EXTERIORWJ
LEFT MULTI-FUNCTION SWITCH (Continued)

COURTESY LAMP
REMOVAL
REMOVAL - BULB
(1) Remove the door trim panel. (Refer to 23 -
BODY/DOOR - FRONT/TRIM PANEL - REMOVAL)
for the service procedures.
(2) Remove the bulb socket from the lamp.
(3) Remove the bulb from the socket.
REMOVAL - LAMP
(1) Remove door trim panel. (Refer to 23 - BODY/
DOOR - FRONT/TRIM PANEL - REMOVAL) for the
procedures.
(2) Disengage the electrical connectors.
(3) Depress the locking tabs and remove the lamp
module.
(4) Remove the bulb socket.
INSTALLATION
INSTALLATION - BULB
(1) Install the bulb in the socket.
(2) Install the bulb socket in the lamp.
(3) Install the door trim panel.
INSTALLATION - LAMP
(1) Install the bulb socket into the lamp module.
(2) Align the lamp module with the door trim
panel.
(3) Snap the lamp module into place.
(4) Install the door panel.
DOME LAMP
REMOVAL
REMOVAL - BULB
(1) Rotate the the grab handle down.
(2) Remove the screws retaining the grab handle/
dome lens.
(3) Remove the grab handle/lens from the module.
(4) Remove the bulb from the lamp terminals.
REMOVAL - LAMP
It will be necessary to partially remove the head-
liner to remove the bulb socket.
(1) Remove the screws holding the grab handle/
lens assembly to the headliner and roof panel.(2) Lower the headliner as needed. (Refer to 23 -
BODY/INTERIOR/HEADLINER - REMOVAL) for the
service procedure.
(3) Separate the lamp socket from the headliner
and roof panel.
(4) Disconnect the wire connector.
INSTALLATION
INSTALLATION - BULB
(1) Insert the bulb into the lamp terminals.
(2) Position the grab handle/lens on the lamp mod-
ule.
(3) Install the screws retaining the grab handle/
lens to the lamp module.
INSTALLATION - LAMP
(1) Position the lamp socket on the headliner and
roof panel.
(2) Connect the wire harness.
(3) Install the headliner.
(4) Position the grab handle/lens on the lamp mod-
ule.
(5) Install the screws retaining the grab handle/
lens into the lamp socket.
DOOR AJAR SWITCH
DESCRIPTION
DESCRIPTION - DOOR AJAR SWITCH
The door ajar switches are integral to the door
latch mechnicism. The front door ajar switches are
actuated by the front door latch mechanisms, and are
hard wired between a body ground and the Driver
Door Module (DDM) or the Passenger Door Module
(PDM). The rear door ajar switches are actuated by
the rear door latch mechanisms, and are hard wired
between a body ground and the Body Control Module
(BCM) through the rear door and body wire har-
nesses.
The door ajar switches cannot be adjusted or
repaired and, if faulty or damaged, the door latch
unit must be replaced. (Refer to 23 - BODY/DOOR -
FRONT/LATCH - REMOVAL) or (Refer to 23 -
BODY/DOORS - REAR/LATCH - REMOVAL) for the
service procedures. For complete circuit diagrams,
refer to the appropriate wiring information.
DESCRIPTION - FLIP UP GLASS AJAR SWITCH
The liftgate flip-up glass ajar switch is integral to
the liftgate flip-up glass latch mechnicism. The lift-
gate flip-up glass ajar switch is actuated by the lift-
gate flip-up glass latch mechanism, and is hard
WJLAMPS/LIGHTING - INTERIOR 8L - 29

wired between a body ground, the Body Control Mod-
ule (BCM) and the rear wiper motor module through
the liftgate and body wire harnesses.
The liftgate flip-up glass ajar switch cannot be
adjusted or repaired and, if faulty or damaged, the
liftgate flip-up glass latch unit must be replaced.
(Refer to 23 - BODY/DECKLID/HATCH/LIFTGATE/
TAILGATE/FLIP-UP GLASS LATCH - REMOVAL)
for the service procedures. For complete circuit dia-
grams, refer to the appropriate wiring information.
DESCRIPTION - LIFTGATE AJAR SWITCH
The two liftgate ajar switches are integral to the
two liftgate latch mechanisms. The two liftgate ajar
switches are actuated by the liftgate latch mecha-
nisms, and are hard wired with each other between a
body ground and the Body Control Module (BCM)
through the liftgate and body wire harnesses.
The liftgate ajar switches cannot be adjusted or
repaired and, if faulty or damaged, the liftgate latch
unit must be replaced. (Refer to 23 - BODY/DECK-
LID/HATCH/LIFTGATE/TAILGATE/LATCH -
REMOVAL) for the service procedures. For complete
circuit diagrams, refer to the appropriate wiring
information.
OPERATION
OPERATION - DOOR AJAR SWITCH
The front door ajar switches close a path to ground
for the DDM or the PDM when a front door is
opened, and opens the ground path when a front door
is closed. The rear door ajar switches close a path to
ground for the BCM when a rear door is opened, and
opens the ground path when a rear door is closed.
The DDM, PDM, or BCM read the switch status then
send the proper switch status messages to other
modules over the Programmable Communications
Interface (PCI) data bus network. The door ajar
switch status message is used by the BCM as an
input for Vehicle Theft Security System (VTSS) oper-
ation.
OPERATION - FLIP UP GLASS AJAR SWITCH
The liftgate flip-up glass ajar switch can close a
path to ground for the BCM and the rear wiper
motor module when the liftgate flip-up glass is
opened, and opens the ground path when the liftgate
flip-up glass is closed. The rear wiper motor module
uses the liftgate flip-up glass ajar switch input to
control the rear wiper operation, and will park the
rear wiper blade if this input indicates that the lift-
gate flip-up glass is ajar. The BCM reads the switch
status then sends the proper switch status message
to other modules over the Programmable Communi-cations Interface (PCI) data bus network. The liftgate
flip-up glass ajar switch status message is used by
the BCM as an input for Vehicle Theft Security Sys-
tem (VTSS) operation.
OPERATION - LIFTGATE AJAR SWITCH
Each of the liftgate ajar switches can close a path
to ground for the BCM when the liftgate is opened,
and opens the ground path when the liftgate is
closed. The BCM reads the switch status then sends
the proper switch status message to other modules
over the Programmable Communications Interface
(PCI) data bus network. The liftgate ajar switch sta-
tus message is used by the BCM as an input for
Vehicle Theft Security System (VTSS) operation.
DIAGNOSIS AND TESTING - DOOR AJAR
SWITCH
The following diagnosis and testing is only
for the chime functions. For interior lamp diag-
nosis, refer to the appropriate wiring informa-
tion.The driver door ajar switch is hard wired to the
Driver Door Module (DDM). The DDM communicates
the switch status to the other modules in the vehicle
on the Programmable Communications Interface
(PCI) data bus network. The following test will diag-
nose a faulty driver door ajar switch and circuits. For
complete circuit diagrams, refer to the appropriate
wiring information.
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) Check that the interior lighting switch on the
control stalk of the left multi-function switch is not
in the dome lamp disable position. Open the driver
side front door and note whether the interior lamps
light. They should light. If OK, refer to Key-In Igni-
tion Switch in the Diagnosis and Testing section of
this group for further diagnosis of the chime warning
system. If not OK, go to Step 2.
(2) Disconnect and isolate the battery negative
cable. Remove the trim panel from the driver front
door and disconnect the 4-way door wire harness con-
nector from the front door latch connector. Check for
continuity between the ground circuit of the 4-way
door wire harness connector and a good ground.
There should be continuity. If OK, go to Step 3. If not
OK, repair the ground circuit.
8L - 30 LAMPS/LIGHTING - INTERIORWJ
DOOR AJAR SWITCH (Continued)

OPERATION
The EVIC has access to both non-switched and
ignition switched sources of battery current so that
some of its features remain operational at any time,
while others may only operate with the ignition
switch in the On position. When the ignition switch
is turned to the On position, the EVIC module VFD
will return to the last function being displayed before
the ignition was turned to the Off position.
The compass/temperature display is the normal
EVIC display. With the ignition switch in the On
position, momentarily depressing and releasing the
C/T (compass/temperature) push button switch will
cause the EVIC to return to the compass/tempera-
ture/trip computer display mode from any other
mode. While in the compass/temperature/trip com-
puter display mode, momentarily depressing and
releasing the Step push button will step through the
available trip computer display options.
The EVIC trip computer features several functions
that can be reset. The functions that can be reset
are: average fuel economy, trip odometer and elapsed
time. With the ignition switch in the On position and
with one of the functions of the trip computer that
can be reset currently displayed, depressing the
Reset push button twice within three seconds will
perform a global reset, and all of the trip computer
information that can be reset will be reset to zero.
With the ignition switch in the On position and the
function that is to be reset currently displayed,
momentarily depressing and releasing the Reset
push button once will perform a local reset, and only
the value of the displayed function will be reset to
zero. A global or local reset will only occur if the
function currently displayed is a function that can be
reset. The distance to service function can also be
reset using the local reset method, but it will reset
back to the Service Interval distance that is set in
the EVIC programmable features mode. Refer to
ELECTRONIC VEHICLE INFORMATION CEN-
TER PROGRAMMINGin the Service Procedures
section of this group for more information on setting
the Service Interval.
For more information on the features, control func-
tions and setting procedures for the EVIC module,
see the owner's manual in the vehicle glove box.
DIAGNOSIS AND TESTING - ELECTRONIC
VEHICLE INFORMATION CENTER
If the problem with the Electronic Vehicle Informa-
tion Center (EVIC) is a temperature reading of 130É
F or -40ÉF shown in the compass/temperature dis-
play, refer toAmbient Temperature Sensor Diag-
nosis and Testingin this group. If the problem with
the EVIC is an inaccurate or scrambled display, refer
toSelf-Diagnostic Testin this group. If the prob-lem with the EVIC is incorrect Vacuum Fluorescent
Display (VFD) dimming levels, use a DRBtscan tool
and the proper Diagnostic Procedures manual to test
for the correct dimming message inputs being
received from the Body Control Module (BCM) over
the Programmable Communications Interface (PCI)
data bus. If the problem is a no-display condition,
use the following procedures. For complete circuit
diagrams, refer toOverhead Consolein Wiring
Diagrams.
(1) Check the fused B(+) fuse in the junction block.
If OK, go to Step 2. If not OK, repair the shorted cir-
cuit or component as required and replace the faulty
fuse.
(2) Check for battery voltage at the fused B(+) fuse
in the junction block. If OK, go to Step 3. If not OK,
repair the open fused B(+) circuit to the fused B(+)
fuse in the PDC as required.
(3) Check the fused ignition switch output (run/
start) fuse in the junction block. If OK, go to Step 4.
If not OK, repair the shorted circuit or component as
required and replace the faulty fuse.
(4) Turn the ignition switch to the On position.
Check for battery voltage at the fused ignition switch
output (run/start) fuse in the junction block. If OK,
go to Step 5. If not OK, repair the open fused ignition
switch output (run/start) circuit to the ignition switch
as required.
(5) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Remove the overhead console. Check for continuity
between the ground circuit cavity of the roof wire
harness connector for the EVIC module and a good
ground. There should be continuity. If OK, go to Step
6. If not OK, repair the open ground circuit to ground
as required.
(6) Connect the battery negative cable. Check for
battery voltage at the fused B(+) circuit cavity of the
roof wire harness connector for the EVIC module. If
OK, go to Step 7. If not OK, repair the open fused
B(+) circuit to the fused B(+) fuse in the junction
block as required.
(7) Turn the ignition switch to the On position.
Check for battery voltage at the fused ignition switch
output (run/start) circuit cavity of the roof wire har-
ness connector for the EVIC module. If OK, refer to
Self-Diagnostic Testbelow for further diagnosis of
the EVIC module and the PCI data bus. If not OK,
repair the open fused ignition switch output (run/
start) circuit to the fuse in the junction block as
required.
SELF-DIAGNOSTIC TEST
A self-diagnostic test is used to determine that the
EVIC module is operating properly, and that all PCI
WJMESSAGE SYSTEMS 8M - 9
ELECTRONIC VEHICLE INFO CENTER (Continued)