2002 JEEP GRAND CHEROKEE Tire

FUEL GAUGE
DESCRIPTION
A fuel gauge is standard equipment on all instru-
ment clusters. The fuel gauge is located in the lower
left corner of the instrument cluster, to the left of the
tachometer. The fuel gauge consists of a movable
gauge needle or pointer controlled by the instrument
cluster circuitry and a fixed 90 degree scale on the
gauge dial face that reads left-to-right from E (or
Empty) to F (or Full). An International Control and
Display Symbol icon for ªFuelº is located on the
gauge dial face. An arrowhead pointed to the left side
of the vehicle is imprinted next to the ªFuelº icon on
the fuel gauge dial face to provide the driver with a
reminder as to the location of the fuel filler access.
The fuel gauge graphics are either white, gray and
orange against a black gauge dial face (base cluster)
or black and gray against a taupe gauge dial face
(premium cluster), making them clearly visible
within the instrument cluster in daylight. When illu-
minated from behind by the panel lamps dimmer
controlled cluster illumination lighting with the exte-
rior lamps turned On, the base cluster white gauge
graphics appear blue-green and the orange graphics
still appear orange, while the premium cluster taupe
gauge dial face appears blue-green with the black
graphics silhouetted against the illuminated back-
ground. The gray gauge graphics for both versions of
the cluster are not illuminated. The orange gauge
needle in the base cluster gauge is internally illumi-
nated, while the black gauge needle in the premium
cluster gauge is not.
Base cluster gauge illumination is provided by
replaceable incandescent bulb and bulb holder units
located on the instrument cluster electronic circuit
board. Premium cluster gauge illumination is pro-
vided by an integral electro-luminescent lamp that is
serviced as a unit with the instrument cluster. The
fuel gauge is serviced as a unit with the instrument
cluster.
OPERATION
The fuel gauge gives an indication to the vehicle
operator of the level of fuel in the fuel tank. This
gauge is controlled by the instrument cluster circuit
board based upon cluster programming and elec-
tronic messages received by the cluster from the
Powertrain Control Module (PCM) over the Program-
mable Communications Interface (PCI) data bus. The
fuel gauge is an air core magnetic unit that receives
battery current on the instrument cluster electronic
circuit board through the fused ignition switch out-
put (run-start) circuit whenever the ignition switch is
in the On or Start positions. The cluster is pro-
grammed to move the gauge needle back to the lowend of the scale after the ignition switch is turned to
the Off position. The instrument cluster circuitry
controls the gauge needle position and provides the
following features:
²Percent Tank Full Message- Each time the
cluster receives a message from the PCM indicating
the percent tank full, the cluster moves the gauge
needle to the relative fuel level position on the gauge
scale. The PCM applies an algorithm to the input
from the fuel tank sender to dampen gauge needle
movement against the negative effect that fuel slosh-
ing within the fuel tank can have on accurate inputs
to the PCM.
²Less Than 12.5 Percent Tank Full Message-
Each time the cluster receives messages from the
PCM indicating the percent tank full is less than
12.5 (one-eighth), the gauge needle is moved to the
proper position on the gauge scale and the low fuel
indicator is illuminated. The low fuel indicator
remains illuminated until the cluster receives mes-
sages from the PCM indicating that the percent tank
full is greater than 12.5 (one-eighth), or until the
ignition switch is turned to the Off position, which-
ever occurs first.
²Less Than Empty Percent Tank Full Mes-
sage- Each time the cluster receives a message from
the PCM indicating the percent tank full is less than
empty, the gauge needle is moved to the far left (low)
end of the gauge scale and the low fuel indicator is
illuminated immediately. This message would indi-
cate that the fuel tank sender input to the PCM is a
short circuit.
²More Than Full Percent Tank Full Message
- Each time the cluster receives a message from the
PCM indicating the percent tank full is more than
full, the gauge needle is moved to the far left (low)
end of the gauge scale and the low fuel indicator is
illuminated immediately. This message would indi-
cate that the fuel tank sender input to the PCM is an
open circuit.
²Communication Error- If the cluster fails to
receive a percent tank full message, it will hold the
gauge needle at the last indication for about twelve
seconds, until a new message is received, or until the
ignition switch is turned to the Off position, which-
ever occurs first. After twelve seconds, the cluster
will return the gauge needle 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 fuel tank
sender to determine the fuel level. The PCM then
applies an algorithm to the input and sends the
WJINSTRUMENT CLUSTER 8J - 21

Base cluster gauge illumination is provided by
replaceable incandescent bulb and bulb holder units
located on the instrument cluster electronic circuit
board. Premium cluster gauge illumination is pro-
vided by an integral electro-luminescent lamp that is
serviced as a unit with the instrument cluster. The
oil pressure gauge is serviced as a unit with the
instrument cluster.
OPERATION
The oil pressure gauge gives an indication to the
vehicle operator of the engine oil pressure. This
gauge is controlled by the instrument cluster circuit
board based upon cluster programming and elec-
tronic messages received by the cluster from the
Powertrain Control Module (PCM) over the Program-
mable Communications Interface (PCI) data bus. The
oil pressure gauge is an air core magnetic unit that
receives battery current on the instrument cluster
electronic circuit board through the fused ignition
switch output (run-start) circuit whenever the igni-
tion switch is in the On or Start positions. The clus-
ter is programmed to move the gauge needle back to
the low end of the scale after the ignition switch is
turned to the Off position. The instrument cluster
circuitry controls the gauge needle position and pro-
vides the following features:
²Engine Oil Pressure Normal Message- Each
time the cluster receives a message from the PCM
indicating the engine oil pressure is within the nor-
mal operating range [above 0.28 kg/cm (above 4
psi), the gauge needle is moved to the relative pres-
sure position of the gauge scale.
²Engine Oil Pressure Low Message- Each
time the cluster receives a message from the PCM
indicating the engine oil pressure is about 0.28
kg/cm or lower (about 4 psi or lower), the gauge
needle is moved to the far left (low) end of the gauge
scale. The gauge needle remains at the low end of
the scale until the cluster receives a message from
the PCM indicating that the engine oil pressure is
about 0.56 kg/cm or higher (about 8 psi or higher).
²Communication Error- If the cluster fails to
receive an engine oil pressure message, it will hold
the gauge needle at the last indication for about
twelve seconds or until a new engine oil pressure
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 oil pres-
sure sensor to determine the engine oil pressure. ThePCM then sends the proper engine oil pressure mes-
sages to the instrument cluster. For further diagnosis
of the oil pressure gauge or the instrument cluster
circuitry that controls the gauge, (Refer to 8 - ELEC-
TRICAL/INSTRUMENT CLUSTER - DIAGNOSIS
AND TESTING). If the instrument cluster turns on
the check gauges indicator due to a low oil pressure
gauge reading, it may indicate that the engine or the
engine oiling system requires service. For proper
diagnosis of the engine oil pressure sensor, the PCM,
the PCI data bus, or the electronic message inputs to
the instrument cluster that control the oil pressure
gauge, a DRBIIItscan tool is required. Refer to the
appropriate diagnostic information.
OVERDRIVE OFF INDICATOR
DESCRIPTION
An overdrive off indicator is standard equipment
on all gasoline engine instrument clusters. The over-
drive off indicator is located in the lower edge of the
tachometer gauge dial face in the instrument cluster.
The overdrive off indicator consists of the words ªO/D
OFFº imprinted on an amber lens. The lens is
located behind a cutout in the opaque layer of the
tachometer gauge dial face overlay. The dark outer
layer of the gauge dial face overlay prevents the indi-
cator from being clearly visible when it is not illumi-
nated. The words ªO/D OFFº appear silhouetted
against an amber field through the translucent outer
layer of the gauge dial face overlay when the indica-
tor 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 overdrive off 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 overdrive off indicator lens is
serviced as a unit with the instrument cluster.
OPERATION
The overdrive off indicator gives an indication to
the vehicle operator when the Off position of the
overdrive off switch has been selected, disabling the
electronically controlled overdrive feature of the auto-
matic transmission. 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 over the Programmable
Communications Interface (PCI) data bus. These
messages are sent by the Powertrain Control Module
(PCM) or by the Transmission Control Module
(TCM), depending on the model of the automatic
transmission. The overdrive off indicator bulb is com-
8J - 26 INSTRUMENT CLUSTERWJ
OIL PRESSURE GAUGE (Continued)

OPERATION
The speedometer gives an indication to the vehicle
operator of the vehicle road speed. This gauge is con-
trolled by the instrument cluster electronic circuit
board based upon cluster programming and elec-
tronic messages received by the cluster from the
Powertrain Control Module (PCM) over the Program-
mable Communications Interface (PCI) data bus. The
speedometer is an air core magnetic unit that
receives battery current on the instrument cluster
electronic circuit board through the fused ignition
switch output (run-start) circuit whenever the igni-
tion switch is in the On or Start positions. The clus-
ter is programmed to move the gauge needle back to
the low end of the scale after the ignition switch is
turned to the Off position. The instrument cluster
circuitry controls the gauge needle position and pro-
vides the following features:
²Vehicle Speed Message- Each time the clus-
ter receives a vehicle speed message from the PCM it
will calculate the correct vehicle speed reading and
position the gauge needle at that speed position on
the gauge scale. The cluster will receive a new vehi-
cle speed message and reposition the gauge pointer
accordingly about every 86 milliseconds. The gauge
needle will continue to be positioned at the actual
vehicle speed position on the gauge scale until the
ignition switch is turned to the Off position.
²Communication Error- If the cluster fails to
receive a speedometer message, it will hold the gauge
needle at the last indication for about six seconds, or
until the ignition switch is turned to the Off position,
whichever occurs first. If a new speed message is not
received after about six seconds, the gauge needle
will return to the far left (low) end of the 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 vehicle speed
information received from the Controller Anti-lock
Brake (CAB) to determine the vehicle road speed,
then sends the proper vehicle speed messages to the
instrument cluster. For further diagnosis of the
speedometer or the instrument cluster circuitry that
controls the gauge, (Refer to 8 - ELECTRICAL/IN-
STRUMENT CLUSTER - DIAGNOSIS AND TEST-
ING). For proper diagnosis of the CAB, the PCM, the
PCI data bus, or the electronic message inputs to the
instrument cluster that control the speedometer, a
DRBIIItscan tool is required. Refer to the appropri-
ate diagnostic information.
TACHOMETER
DESCRIPTION
A tachometer is standard equipment on all instru-
ment clusters. The tachometer is located to the left of
the speedometer in the instrument cluster. The
tachometer consists of a movable gauge needle or
pointer controlled by the instrument cluster circuitry,
and a fixed 255 degree scale on the gauge dial face
that reads left-to-right from 0 to 7 for gasoline
engines, or from 0 to 6 for diesel engines. The text ªX
1000º (base cluster) or ªRPM X 1000º (premium clus-
ter) imprinted on the cluster overlay directly below
the hub of the tachometer needle identifies that each
number on the tachometer scale is to be multiplied
by 1000 rpm. The gasoline engine tachometer has a
red zone beginning at 5800 RPM, while the red zone
for the diesel engine tachometer begins at 4200 RPM.
The tachometer in the premium version cluster for
certain engine and market applications also includes
red text located in the center of the gauge dial face
just above the hub of the tachometer needle that
specifies a special fuel requirement.
The tachometer graphics are either white, gray
and orange against a black gauge dial face (base
cluster) or black, gray and red against a taupe gauge
dial face (premium cluster), making them clearly vis-
ible within the instrument cluster in daylight. When
illuminated from behind by the panel lamps dimmer
controlled cluster illumination lighting with the exte-
rior lamps turned On, the base cluster white gauge
graphics appear blue-green and the orange graphics
still appear orange, while the premium cluster taupe
gauge dial face appears blue-green with the black
graphics silhouetted against the illuminated back-
ground and the red graphics still appear red. The
gray gauge graphics for both versions of the cluster
are not illuminated. The orange gauge needle in the
base cluster gauge is internally illuminated, while
the black gauge needle in the premium cluster gauge
is not.
Base cluster gauge illumination is provided by
replaceable incandescent bulb and bulb holder units
located on the instrument cluster electronic circuit
board. Premium cluster gauge illumination is pro-
vided by an integral electro-luminescent lamp that is
serviced as a unit with the instrument cluster. The
tachometer is serviced as a unit with the instrument
cluster.
OPERATION
The tachometer gives an indication to the vehicle
operator of the engine speed. This gauge is controlled
by the instrument cluster electronic circuit board
based upon cluster programming and electronic mes-
sages received by the cluster from the Powertrain
WJINSTRUMENT CLUSTER 8J - 31
SPEEDOMETER (Continued)

Control Module (PCM) over the Programmable Com-
munications Interface (PCI) data bus. The tachome-
ter is an air core magnetic unit that receives battery
current on the instrument cluster electronic circuit
board through the fused ignition switch output (run-
start) circuit whenever the ignition switch is in the
On or Start positions. The cluster is programmed to
move the gauge needle back to the low end of the
scale after the ignition switch is turned to the Off
position. The instrument cluster circuitry controls
the gauge needle position and provides the following
features:
²Engine Speed Message- Each time the cluster
receives an engine speed message from the PCM it
will calculate the correct engine speed reading and
position the gauge needle at that speed position on
the gauge scale. The cluster will receive a new
engine speed message and reposition the gauge
pointer accordingly about every 86 milliseconds. The
gauge needle will continue to be positioned at the
actual engine speed position on the gauge scale until
the ignition switch is turned to the Off position.
²Communication Error- If the cluster fails to
receive an engine speed message, it will hold the
gauge needle at the last indication for about six sec-
onds, or until the ignition switch is turned to the Off
position, whichever occurs first. If a new engine
speed message is not received after about six sec-
onds, the gauge needle will return to the far left
(low) end of the 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 crankshaft posi-
tion sensor to determine the engine speed, then
sends the proper engine speed messages to the
instrument cluster. For further diagnosis of the
tachometer or the instrument cluster circuitry that
controls the gauge, (Refer to 8 - ELECTRICAL/IN-
STRUMENT CLUSTER - DIAGNOSIS AND TEST-
ING). For proper diagnosis of the crankshaft position
sensor, the PCM, the PCI data bus, or the electronic
message inputs to the instrument cluster that control
the tachometer, a DRBIIItscan tool is required.
Refer to the appropriate diagnostic information.
TRANS TEMP INDICATOR
DESCRIPTION
A transmission over-temperature indicator is stan-
dard equipment on all gasoline engine instrument
clusters. The transmission over-temperature indica-
tor is located near the lower right corner of theinstrument cluster, to the right of the speedometer.
The transmission over-temperature indicator consists
of the words ªTRANS OVER TEMPº imprinted on an
amber 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 indi-
cator from being clearly visible when it is not illumi-
nated. The words ªTRANS OVER TEMPº appear
silhouetted against an amber field through the trans-
lucent outer layer of the overlay when the indicator
is illuminated from behind by a replaceable incandes-
cent bulb and bulb holder unit located on the instru-
ment cluster electronic circuit board. The
transmission over-temperature indicator lens is ser-
viced as a unit with the instrument cluster lens, hood
and mask unit.
OPERATION
The transmission over-temperature indicator gives
an indication to the vehicle operator when the trans-
mission fluid temperature is excessive, which may
lead to accelerated transmission component wear or
failure. This indicator is controlled by a transistor on
the instrument cluster electronic circuit board based
upon cluster programming and electronic messages
received by the cluster over the Programmable Com-
munications Interface (PCI) data bus. These mes-
sages are sent by the Powertrain Control Module
(PCM) or by the Transmission Control Module
(TCM), depending on the model of the automatic
transmission. The transmission over-temperature
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 transmission over-tempera-
ture indicator for the following reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the transmission over-tem-
perature indicator is illuminated for about three sec-
onds as a bulb test.
²Trans Over-Temp Indicator Lamp-On Mes-
sage- Each time the cluster receives a trans over-
temp indicator lamp-on message from the PCM or
TCM indicating that the transmission fluid tempera-
ture is 135É C (275É F) or higher, the transmission
over-temperature indicator will be illuminated. The
indicator remains illuminated until the cluster
receives a trans over-temp indicator lamp-off mes-
sage from the PCM or TCM, or until the ignition
8J - 32 INSTRUMENT CLUSTERWJ
TACHOMETER (Continued)

ing the system voltage is high (system voltage is
about sixteen volts or higher), the gauge needle is
moved to the relative voltage position in the red zone
of the gauge scale and the check gauges indicator is
illuminated. The gauge needle remains in the red
zone and the check gauges indicator remains illumi-
nated until the cluster receives a message from the
PCM indicating there is no high system voltage con-
dition (system voltage is below about sixteen volts,
but higher than about eleven volts).
²Communication Error- If the cluster fails to
receive a system voltage message, it will hold the
gauge needle at the last indication for about twelve
seconds, until a new message is received, or until the
ignition switch is turned to the Off position, which-
ever occurs first. After twelve seconds, the cluster
will return the gauge needle 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 to con-
firm the functionality of the gauge and the cluster
control circuitry.
The PCM continually monitors the system voltage
to control the generator output. The PCM then sends
the proper system voltage messages to the instru-
ment cluster. For further diagnosis of the voltage
gauge or the instrument cluster circuitry that con-
trols the gauge, (Refer to 8 - ELECTRICAL/INSTRU-
MENT CLUSTER - DIAGNOSIS AND TESTING). If
the instrument cluster turns on the check gauges
indicator due to a system voltage low or high condi-
tion, it may indicate that the charging system
requires service. For proper diagnosis of the charging
system, the PCI data bus, or the electronic message
inputs to the instrument cluster that control the volt-
age gauge, a DRBIIItscan tool is required. Refer to
the appropriate diagnostic information.
WAIT-TO-START INDICATOR
DESCRIPTION
A wait-to-start indicator is only found in the
instrument clusters of vehicles equipped with an
optional diesel engine. The wait-to-start indicator is
located near the lower edge of the tachometer gauge
dial face, to the right of center. The wait-to-start
indicator consists of an International Control and
Display Symbol icon for ªDiesel Preheatº imprinted
on an amber lens. The lens is located behind a cutout
in the opaque layer of the tachometer gauge dial face
overlay. The dark outer layer of the gauge dial face
overlay prevents the icon from being clearly visible
when the indicator is not illuminated. The icon
appears silhouetted against an amber field throughthe translucent outer layer of the gauge dial face
overlay when the indicator is illuminated from
behind by a replaceable incandescent bulb and bulb
holder unit located on the instrument cluster elec-
tronic circuit board. The wait-to-start indicator lens
is serviced as a unit with the instrument cluster.
OPERATION
The wait-to-start indicator gives an indication to
the vehicle operator when the diesel engine glow
plugs are energized in their preheat operating mode.
This indicator is controlled by a transistor on the
instrument cluster circuit board based upon cluster
programming and electronic messages received by
the cluster from the Powertrain Control Module
(PCM) over the Programmable Communications
Interface (PCI) data bus. The wait-to-start indicator
bulb is completely controlled by the instrument clus-
ter 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 indi-
cator will always be off when the ignition switch is in
any position except On or Start. The bulb only illu-
minates when it is switched to ground by the instru-
ment cluster transistor. The instrument cluster will
turn on the wait-to-start indicator for the following
reasons:
²Wait-To-Start Indicator Lamp-On Message-
Each time the cluster receives a wait-to-start indica-
tor lamp-on message from the PCM indicating the
glow plugs are heating and the driver must wait to
start the engine, the wait-to-start indicator will be
illuminated. The indicator remains illuminated until
the cluster receives a wait-to-start indicator lamp-off
message, or until the ignition switch is turned to the
Off position, whichever occurs first.
²Actuator Test- Each time the cluster is put
through the actuator test, the wait-to-start 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 PCM continually monitors the ambient tem-
perature and the glow plug pre-heater circuits to
determine how long the glow plugs must be heated in
the pre-heat operating mode. The PCM then sends
the proper wait-to-start indicator lamp-on and lamp-
off messages to the instrument cluster. If the wait-to-
start indicator fails to light during the actuator test,
replace the bulb with a known good unit. For further
diagnosis of the wait-to-start indicator or the instru-
ment cluster circuitry that controls the indicator,
(Refer to 8 - ELECTRICAL/INSTRUMENT CLUS-
TER - DIAGNOSIS AND TESTING). For proper
diagnosis of the glow plug pre-heater control circuits,
the PCM, the PCI data bus, or the electronic message
WJINSTRUMENT CLUSTER 8J - 35
VOLTAGE GAUGE (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)

ness connector for the multi-function switch and the
instrument panel wire harness connector for the
BCM. There should be continuity. If OK, go to Step 3.
If not OK, repair the open headlamp switch mux cir-
cuit.
(3) Check for continuity between the headlamp
switch return 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 4. If not OK, repair the shorted headlamp
switch return circuit.
(4) Check for continuity between the headlamp
switch return circuit of the instrument panel wire
harness connector for the multi-function switch and
the instrument panel wire harness connector for the
BCM. There should be continuity. If OK, use a
DRBIIItscan tool and the proper Diagnostic Proce-
dures manual to test the BCM. If not OK, repair the
open headlamp switch return circuit.
HEADLAMP UNIT
REMOVAL
(1) Remove the jack screw attaching the top of
headlamp to the headlamp mounting module (Fig.
14).
(2) Grasp upper inboard and lower outboard cor-
ners of headlamp (Fig. 15) and pull headlamp out-
ward.
(3) Remove all of the bulb sockets from headlamp
module.
(4) Separate the headlamp from vehicle.
INSTALLATION
CAUTION: Do not touch the bulb glass with fingers
or other oily surfaces. Reduced bulb life will result.
(1) Install all of the bulb sockets in headlamp mod-
ule.
(2) Position the headlamp on the vehicle and align
the ball studs with the sockets.
(3) Push the headlamp inward to secure the ball
studs with the sockets.
(4) Install the jack screw attaching the top of
headlamp to the headlamp mounting module.
ADJUSTMENTS
VEHICLE PREPARATION FOR LAMP ALIGNMENT
(1) Verify headlamp dimmer switch and high beam
indicator operation.
(2) Correct defective components that could hinder
proper lamp alignment.
(3) Verify proper tire inflation.
(4) Clean lamp lenses.
(5) Verify that luggage area is not heavily loaded.
(6) Fuel tank should be FULL. Add 2.94 kg (6.5
lbs.) of weight over the fuel tank for each estimated
gallon of missing fuel.
LAMP ALIGNMENT SCREEN PREPARATION
(1) Position vehicle on a level surface perpendicu-
lar to a flat wall 7.62 meters (25 ft) away from front
of headlamp lens (Fig. 16).
(2) If necessary, tape a line on the floor 7.62
meters (25 ft) away from and parallel to the wall.
(3) Measure from the floor up 1.27 meters (5 ft)
and tape a line on the wall at the centerline of the
vehicle. Sight along the centerline of the vehicle
Fig. 14 Headlamp Jackscrew
1 - JACKSCREW
2 - HEADLAMP
Fig. 15 Headlamp Removal
1 - HEADLAMP
8L - 16 LAMPS/LIGHTING - EXTERIORWJ
HEADLAMP SWITCH (Continued)

INSTALLATION
(1) Install the license plate lamps, and the flip up
glass switch, if equipped.
(2) Connect the wire harnesses for the license
plate lamps and the flip up glass switch.
(3) Install the lamp housing/trim panel on the lift-
gate.
LEFT MULTI-FUNCTION
SWITCH
DESCRIPTION
The left multi-function switch, its mounting provi-
sions, and its electrical connections are all concealed
beneath the steering column shrouds, just below the
steering wheel (Fig. 22).
A single connector with eleven terminal pins is
located on the back of the switch housing and con-
nects the switch to the vehicle electrical system. The
left multi-function switch supports the following exte-
rior lighting functions:
²Auto Headlamps
²Front Fog Lamps
²Hazard Warning Control
²Headlamps
²Headlamp Beam Selection
²Headlamp Optical Horn
²Park Lamps
²Rear Fog Lamps
²Turn Signal Control
The left multi-function switch also supports the fol-
lowing interior lighting functions:
²Panel Lamps Dimming
²Interior Lamps Defeat²Interior Lamps On
²Parade Mode
The left multi-function switch cannot be adjusted
or repaired. If any function of the switch is faulty, or
if the switch is damaged, the entire switch unit must
be replaced.
OPERATION
The left multi-function switch uses a combination
of resistor multiplexed and conventionally switched
outputs to control the many functions and features it
provides using a minimal number of hard wired cir-
cuits. The switch is grounded to the chassis beneath
the center floor console, just forward of the Airbag
Control Module (ACM). Following are descriptions of
the how the left multi-function switch operates to
control the many exterior lighting functions and fea-
tures it provides:
²Auto Headlamps- The automatic headlamps
feature is provided by the Body Control Module
(BCM), which monitors an input from a photodiode
sensor located on the top of the instrument panel to
detect ambient light levels whenever the ignition
switch is in the On position. Based upon the multi-
plexed input from the left multi-function switch and
the input of the photodiode sensor, the BCM controls
outputs to the park lamp and headlamp relays to
illuminate or extinguish all exterior lighting.
²Front Fog Lamps- The Body Control Module
(BCM) monitors the left multi-function switch then,
based upon that switched ground input, controls an
output to the front fog lamp relay to illuminate or
extinguish the front fog lamps.
Fig. 21 License Plate Lamp Housing
1 - LICENSE PLATE LAMP
2 - CONNECTOR
3 - LIFTGATE
Fig. 22 Left (Lighting) Multi-Function Switch
1 - EXTERIOR LIGHTING CONTROL
2 - INTERIOR LIGHTING CONTROL
3 - CONTROL STALK
4 - HAZARD WARNING BUTTON
5 - CANCEL ACTUATOR
6 - LEFT (LIGHTING) MULTI-FUNCTION SWITCH
WJLAMPS/LIGHTING - EXTERIOR 8L - 19
LICENSE PLATE LAMP UNIT (Continued)