2003 JEEP GRAND CHEROKEE Dimmer switch

instrument cluster logic circuit, and that logic will
only allow this indicator to operate when the instru-
ment 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 MIL for the fol-
lowing reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the MIL is illuminated for
about three seconds as a bulb test.
²MIL Lamp-On Message- Each time the clus-
ter receives a MIL lamp-on message from the PCM,
the indicator will be illuminated. The indicator can
be flashed on and off, or illuminated solid, as dic-
tated by the PCM message. For some DTC's, if a
problem does not recur, the PCM will send a MIL
lamp-off message automatically. Other DTC's may
require that a fault be repaired and the PCM be
reset before a MIL lamp-off message will be sent. For
more information on the PCM and the DTC set and
reset parameters, (Refer to 25 - EMISSIONS CON-
TROL - OPERATION).
²Communication Error- If the cluster receives
no MIL lamp-on or lamp-off messages from the PCM
for twenty consecutive seconds, the MIL is illumi-
nated by the instrument cluster. The indicator
remains controlled and illuminated by the cluster
until a valid MIL lamp-on or lamp-off message is
received from the PCM.
²Actuator Test- Each time the cluster is put
through the actuator test, the MIL will be turned on
for the duration of the test to confirm the functional-
ity of the bulb and the cluster control circuitry.
The PCM continually monitors each of the many
fuel and emissions system circuits and sensors to
decide whether the system is in good operating con-
dition. The PCM then sends the proper MIL lamp-on
or lamp-off messages to the instrument cluster. If the
MIL fails to light during the bulb test, replace the
bulb with a known good unit. For further diagnosis of
the MIL or the instrument cluster circuitry that con-
trols the indicator, (Refer to 8 - ELECTRICAL/IN-
STRUMENT CLUSTER - DIAGNOSIS AND
TESTING). If the instrument cluster turns on the
MIL after the bulb test, it may indicate that a mal-
function has occurred and that the fuel and emis-
sions system may require service. For proper
diagnosis of the fuel and emissions systems, the
PCM, the PCI data bus, or the electronic message
inputs to the instrument cluster that control the
MIL, a DRBIIItscan tool is required. Refer to the
appropriate diagnostic information.ODOMETER
DESCRIPTION
An odometer and trip odometer are standard
equipment in all instrument clusters. The odometer
and trip odometer information are displayed in a
common electronic, blue-green Vacuum-Fluorescent
Display (VFD), which is located in the lower edge of
the speedometer dial face in the instrument cluster
and, when illuminated, is visible through a small
window cutout in the gauge overlay. However, the
odometer and trip odometer information are not dis-
played simultaneously. The trip odometer reset
switch on the instrument cluster electronic circuit
board toggles the display between odometer and trip
odometer modes by depressing the odometer/trip
odometer switch button that extends through the
lower edge of the cluster lens to the right of the
speedometer.
All odometer and trip odometer distance informa-
tion is stored in the instrument cluster memory. This
distance information can be increased when the
proper inputs are provided to the instrument cluster,
but the distance information cannot be decreased.
The odometer can display values up to 999,999 kilo-
meters (999,999 miles). The odometer will not roll
over, but will latch at the maximum value. The trip
odometer can display values up to 999.9 kilometers
(999.9 miles) before it rolls over to zero. The odome-
ter display does not have a decimal point and will
not show values less than a full unit (kilometer or
mile), the trip odometer display does have a decimal
point and will show tenths of a unit (kilometer or
mile).
The unit of measure for the odometer and trip
odometer display is not shown in the VFD. The unit
of measure for the odometer/trip odometer is selected
at the time that the instrument cluster is manufac-
tured, and cannot be changed. If the instrument clus-
ter has a kilometers-per-hour primary speedometer
scale, the odometer/trip odometer registers kilome-
ters; and, if the cluster features a miles-per-hour pri-
mary speedometer scale, the odometer/trip odometer
registers miles.
During daylight hours (exterior lamps Off) the
VFD is illuminated at full brightness for clear visibil-
ity. At night (exterior lamps are On) the instrument
cluster converts an electronic dimming level message
received from the Body Control Module (BCM) over
the Programmable Communications Interface (PCI)
data bus to a digital dimming level signal for control-
ling the lighting level of the VFD. However, a
ªParadeº mode position of the panel lamps dimmer
control ring on the control stalk of the left (lighting)
multi-function switch allows the VFD to be illumi-
8J - 24 INSTRUMENT CLUSTERWJ
MALFUNCTION INDICATOR LAMP (MIL) (Continued)

nated at full brightness if the exterior lamps are
turned On during daylight hours.
The VFD, the trip odometer switch, and the trip
odometer switch button are serviced as a unit with
the instrument cluster.
OPERATION
The odometer and trip odometer give an indication
to the vehicle operator of the distance the vehicle has
traveled. This gauge is controlled by the instrument
cluster electronic circuitry based upon cluster pro-
gramming and electronic messages received by the
cluster from the Powertrain Control Module (PCM)
over the Programmable Communications Interface
(PCI) data bus. The odometer and trip odometer
information is displayed by the instrument cluster
Vacuum Fluorescent Display (VFD). The VFD will
only display odometer or trip odometer information
after the ignition switch is turned to the On or Start
positions, and will display the information in the
odometer or trip odometer mode based upon the
selection that was active when the ignition switch
was last turned to the Off position. The instrument
cluster circuitry controls the VFD and provides the
following features:
²Odometer/Trip Odometer Display Toggling-
Actuating the trip odometer reset switch button
momentarily with the ignition switch in the On posi-
tion will toggle the display between the odometer and
trip odometer information. Each time the ignition
switch is turned to the On or Start positions, the dis-
play will automatically return to the last mode
selected (odometer or trip odometer) before the igni-
tion switch was turned to the Off position.
²Trip Odometer Reset- When the trip odome-
ter reset switch button is depressed and held for
longer than about two seconds with the ignitions
switch in the On or Start positions, the trip odometer
will be reset to 000.0 kilometers (miles). The VFD
must be displaying the current trip odometer infor-
mation in order for the trip odometer information to
be reset.
²Communication Error- If the cluster fails to
receive a distance message during normal operation,
it will hold and display the last data received until
the ignition switch is turned to the Off position. If
the cluster does not receive a distance message
within one second after the ignition switch is turned
to the On position, it will display the last distance
message stored in the cluster memory. If it is deter-
mined that the distance information stored in the
cluster memory is corrupt, it will display ª------º in
the VFD. If the cluster is unable to display distance
information due to an error internal to the cluster,
the VFD display will be blank.²Actuator Test- Each time the cluster is put
through the actuator test, the VFD will step sequen-
tially through a display of ª000000º through
ª999999º, then display the cluster software version
number to confirm the functionality of the VFD and
the cluster control circuitry.
The PCM continually monitors the vehicle speed
pulse information received from the vehicle speed
sensor, then sends the proper distance messages to
the instrument cluster. For further diagnosis of the
odometer/trip odometer or the instrument cluster cir-
cuitry that controls these functions, (Refer to 8 -
ELECTRICAL/INSTRUMENT CLUSTER - DIAGNO-
SIS AND TESTING). For proper diagnosis of the
vehicle speed sensor, the PCM, the PCI data bus, or
the electronic message inputs to the instrument clus-
ter that control the odometer/trip odometer, a
DRBIIItscan tool is required. Refer to the appropri-
ate diagnostic information.
OIL PRESSURE GAUGE
DESCRIPTION
An oil pressure gauge is standard equipment on all
instrument clusters. The oil pressure gauge is located
in the upper right corner of the instrument cluster, to
the right of the speedometer. The oil pressure gauge
consists of a movable gauge needle or pointer con-
trolled by the instrument cluster circuitry and a fixed
90 degree scale on the gauge dial face that reads left-
to-right from 0 kg/cm to 5.4 kg/cm (metric cluster
for gasoline engines), from 0 kg/cm to 8.3 kg/cm
(metric cluster for diesel engines), or from 0 psi to 80
psi (U.S. cluster), depending upon the market for
which the vehicle is manufactured. An International
Control and Display Symbol icon for ªEngine Oilº is
located on the gauge dial face.
The oil pressure 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.
WJINSTRUMENT CLUSTER 8J - 25
ODOMETER (Continued)

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)

pletely controlled by the instrument cluster logic cir-
cuit, 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 overdrive off indicator for the following
reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the overdrive off indicator
is illuminated for about three seconds as a bulb test.
²Overdrive Off Indicator Lamp-On Message-
Each time the cluster receives an overdrive off indi-
cator lamp-on message from the PCM or TCM indi-
cating that the Off position of the overdrive off
switch has been selected, the overdrive off indicator
will be illuminated. The indicator remains illumi-
nated until the cluster receives an overdrive off indi-
cator lamp-off message from the PCM or TCM, 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 overdrive off 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 or TCM continually monitors the over-
drive off switch to determine the proper outputs to
the automatic transmission. The PCM or TCM then
sends the proper overdrive off indicator lamp-on or
lamp-off messages to the instrument cluster. If the
overdrive off indicator fails to light during the bulb
test, replace the bulb with a known good unit. For
further diagnosis of the overdrive off indicator or the
instrument cluster circuitry that controls the indica-
tor, (Refer to 8 - ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND TESTING). For
proper diagnosis of the overdrive control system, the
PCM, the TCM, the PCI data bus, or the electronic
message inputs to the instrument cluster that control
the overdrive off indicator, a DRBIIItscan tool is
required. Refer to the appropriate diagnostic infor-
mation.
REAR FOG LAMP INDICATOR
DESCRIPTION
A rear fog lamp indicator is standard equipment on
all instrument clusters, but is only functional on
vehicles equipped with optional rear fog lamps,
which are available only in certain international
markets where they are required. The rear fog lampindicator is located on the left edge of the instrument
cluster, to the left of the tachometer. The rear fog
lamp indicator consists of an International Control
and Display Symbol icon for ªRear Fog Lightº
imprinted on an amber lens. The lens is located
behind a cutout in the opaque layer of the instru-
ment cluster overlay. The dark outer layer of the
overlay prevents the indicator from being clearly vis-
ible when it is not illuminated. The icon appears sil-
houetted against an amber 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 rear 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 rear fog lamp indicator lens is
serviced as a unit with the instrument cluster lens,
hood and mask unit.
OPERATION
The rear fog lamp indicator gives an indication to
the vehicle operator whenever the rear fog lamps are
illuminated. This indicator is controlled by a transis-
tor on the instrument cluster electronic 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 rear 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 rear fog lamp
indicator for the following reasons:
²Rear Fog Lamp Indicator Lamp-On Mes-
sage- Each time the cluster receives a rear fog lamp
indicator lamp-on message from the BCM indicating
that the rear fog lamps are turned On, the rear fog
lamp indicator will be illuminated. The indicator
remains illuminated until the cluster receives a rear
fog lamp indicator lamp-off message from the BCM.
²Actuator Test- Each time the cluster is put
through the actuator test, the rear fog lamp 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 exterior light-
ing (left multi-function) switch to determine the
proper outputs to the rear fog lamp relay. The BCM
WJINSTRUMENT CLUSTER 8J - 27
OVERDRIVE OFF INDICATOR (Continued)

Programmable Communications Interface (PCI) data
bus. The SKIS 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 battery current input
on the fused ignition switch output (run-start) cir-
cuit. 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 switched
to ground by the instrument cluster transistor. The
instrument cluster will turn on the SKIS indicator
for the following reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position, the SKIM tells the cluster
to illuminate the SKIS indicator for about three sec-
onds as a bulb test.
²SKIS Indicator Lamp-On Message- Each
time the cluster receives a SKIS indicator lamp-on
message from the SKIM, the SKIS indicator will be
illuminated. The indicator can be flashed on and off,
or illuminated solid, as dictated by the SKIM mes-
sage. For more information on the SKIS and the
SKIS indicator control parameters, (Refer to 8 -
ELECTRICAL/VEHICLE THEFT SECURITY -
OPERATION). The indicator remains illuminated
until the cluster receives a SKIS indicator lamp-off
message from the SKIM, or until the ignition switch
is turned to the Off position, whichever occurs first.
²Communication Error- If the cluster receives
no SKIS indicator lamp-on or lamp-off messages from
the SKIM for twenty consecutive seconds, the SKIS
indicator is illuminated by the instrument cluster.
The indicator remains controlled and illuminated by
the cluster until a valid SKIS indicator lamp-on or
lamp-off message is received from the SKIM.
²Actuator Test- Each time the cluster is put
through the actuator test, the SKIS indicator will be
turned on for the duration of the test to confirm the
functionality of the bulb and the cluster control cir-
cuitry.
The SKIM performs a self-test each time the igni-
tion switch is turned to the On position to decide
whether the system is in good operating condition
and whether a valid key is present in the ignition
lock cylinder. The SKIM then sends the proper SKIS
indicator lamp-on or lamp-off messages to the instru-
ment cluster. If the SKIS indicator fails to light dur-
ing the bulb test, replace the bulb with a known good
unit. For further diagnosis of the SKIS indicator or
the instrument cluster circuitry that controls the
indicator, (Refer to 8 - ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND TESTING). If the
instrument cluster flashes the SKIS indicator upon
ignition On, or turns on the SKIS indicator solid
after the bulb test, it indicates that a SKIS malfunc-
tion has occurred or that the SKIS is inoperative. Forproper diagnosis of the SKIS, the PCI data bus, or
the electronic message inputs to the instrument clus-
ter that control the SKIS indicator, a DRBIIItscan
tool is required. Refer to the appropriate diagnostic
information.
SPEEDOMETER
DESCRIPTION
A speedometer is standard equipment on all instru-
ment clusters. The speedometer is located to the
right of the tachometer in the instrument cluster.
The speedometer consists of a movable gauge needle
or pointer controlled by the instrument cluster cir-
cuitry, and a fixed 255 degree primary scale on the
gauge dial face that reads left-to-right either from 0
to 120 mph, from 0 to 200 km/h, or from 0 to 220
km/h, depending upon the market for which the vehi-
cle is manufactured. Most models also have a smaller
secondary inner scale on the gauge dial face that pro-
vides the equivalent opposite measurement units
from the primary scale. Text appearing in the center
of the gauge dial face just beneath the hub of the
speedometer needle abbreviates the unit of measure
for the primary scale in all upper case letters (i.e.:
MPH or KM/H). On models with a secondary scale,
the abbreviation for that scale follows the abbrevia-
tion for the primary scale in all lower case letters
(i.e.: mph or km/h).
The speedometer 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
speedometer is serviced as a unit with the instru-
ment cluster.
8J - 30 INSTRUMENT CLUSTERWJ
SKIS INDICATOR (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)

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.
(1) Disconnect and isolate the battery negative
cable. Remove the instrument cluster from the
instrument panel and disconnect the instrument
panel wire harness for the instrument cluster from
the cluster connector receptacle.
(2) Reconnect the battery negative cable. Activate
the hazard warning system by moving the hazard
warning switch button to the On position. Check for
battery voltage at the inoperative (right or left) turn
signal circuit cavity of the instrument panel wire
harness connector for the instrument cluster. There
should be a switching (on and off) battery voltage sig-
nal present. If OK, replace the faulty (right or left)
turn signal indicator bulb. If not OK, repair the open
(right or left) turn signal circuit between the instru-
ment cluster and the combination flasher in the
Junction Block (JB) as required.
VOLTAGE GAUGE
DESCRIPTION
A voltage gauge is standard equipment on all
instrument clusters. The voltage gauge is located in
the upper left corner of the instrument cluster, to the
left of the tachometer. The voltage 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 9 volts to 19 volts. An International Control and
Display Symbol icon for ªBattery Charging Condi-
tionº is located on the gauge dial face.
The voltage gauge 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
voltage gauge is serviced as a unit with the instru-
ment cluster.
OPERATION
The voltage gauge gives an indication to the vehi-
cle operator of the electrical system voltage. 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
voltage 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:
²System Voltage Message- Each time the clus-
ter receives a message from the PCM indicating the
system voltage, the cluster moves the gauge needle to
the relative voltage level position on the gauge scale.
²System Voltage Low Message- Each time the
cluster receives a message from the PCM indicating
the system voltage is low (system voltage is about
eleven volts or lower), the gauge needle is moved to
the relative voltage position in the red zone of the
gauge scale and the check gauges indicator is illumi-
nated. The gauge needle remains in the red zone and
the check gauges indicator remains illuminated until
the cluster receives a message from the PCM indicat-
ing there is no low system voltage condition (system
voltage is above about eleven volts, but lower than
about sixteen volts).
²System Voltage High Message- Each time
the cluster receives a message from the PCM indicat-
8J - 34 INSTRUMENT CLUSTERWJ
TURN SIGNAL INDICATOR (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)