2002 JEEP LIBERTY sensor

illuminates when it is provided a path to ground by
the instrument cluster transistor. The instrument
cluster will turn on the ABS indicator for the follow-
ing reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the ABS indicator is illu-
minated by the cluster for about three seconds as a
bulb test.
²ABS Lamp-On Message- Each time the clus-
ter receives a lamp-on message from the CAB, the
ABS indicator will be illuminated. The indicator
remains illuminated until the cluster receives a
lamp-off message from the CAB, or until the ignition
switch is turned to the Off position, whichever occurs
first.
²Communication Error- If the cluster receives
no lamp-on or lamp-off messages from the CAB for
six consecutive seconds, the ABS indicator is illumi-
nated. The indicator remains illuminated until the
cluster receives a valid message from the CAB, or
until the ignition switch is turned to the Off position,
whichever occurs first.
²Actuator Test- Each time the instrument clus-
ter is put through the actuator test, the ABS indica-
tor will be turned on, then off again during the bulb
check portion of the test to confirm the functionality
of the LED and the cluster control circuitry.
²ABS Diagnostic Test- The ABS indicator is
blinked on and off by lamp-on and lamp-off messages
from the CAB during the performance of the ABS
diagnostic tests.
The CAB continually monitors the ABS circuits
and sensors to decide whether the system is in good
operating condition. The CAB then sends the proper
lamp-on or lamp-off messages to the instrument clus-
ter. If the CAB sends a lamp-on message after the
bulb test, it indicates that the CAB has detected a
system malfunction and/or that the ABS system has
become inoperative. The CAB will each store a Diag-
nostic Trouble Code (DTC) for any malfunction it
detects. Each time the ABS indicator fails to light
due to an open or short in the cluster ABS indicator
circuit, the cluster sends a message notifying the
CAB of the condition, then the instrument cluster
and the CAB will each store a DTC. For proper diag-
nosis of the antilock brake system, the CAB, the PCI
data bus, or the message inputs to the instrument
cluster that control the ABS indicator, a DRBIIIt
scan tool is required. Refer to the appropriate diag-
nostic information.AIRBAG INDICATOR
DESCRIPTION
An airbag indicator is standard equipment on all
instrument clusters. However, the instrument cluster
is programmed to automatically enable this indicator
only on vehicles equipped with the airbag system,
which is not available in some markets. The airbag
indicator is located above the fuel gauge and to the
left of the tachometer in the instrument cluster. The
airbag indicator consists of a stencil-like cutout of the
words ªAIR BAGº 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. A red Light Emitting
Diode (LED) behind the cutout in the opaque layer of
the overlay causes the ªAIR BAGº text to appear in
red through the translucent outer layer of the over-
lay when it is illuminated from behind by the LED,
which is soldered onto the instrument cluster elec-
tronic circuit board. The airbag indicator is serviced
as a unit with the instrument cluster.
OPERATION
The airbag indicator gives an indication to the
vehicle operator when the airbag system is faulty or
inoperative. The airbag indicator is controlled by a
transistor on the instrument cluster circuit board
based upon cluster programming and electronic mes-
sages received by the cluster from the Airbag Control
Module (ACM) over the Programmable Communica-
tions Interface (PCI) data bus. The airbag indicator
Light Emitting Diode (LED) 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 LED will always be off when the
ignition switch is in any position except On or Start.
The LED only illuminates when it is provided a path
to ground by the instrument cluster transistor. The
instrument cluster will turn on the airbag indicator
for the following reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the airbag indicator is illu-
minated for about six seconds. The entire six second
bulb test is a function of the ACM.
²ACM Lamp-On Message- Each time the clus-
ter receives a lamp-on message from the ACM, the
airbag indicator will be illuminated. The indicator
remains illuminated for about twelve seconds or until
the cluster receives a lamp-off message from the
ACM, whichever is longer.
²Communication Error- If the cluster receives
no airbag messages for six consecutive seconds, the
airbag indicator is illuminated. The indicator
8J - 12 INSTRUMENT CLUSTERKJ
ABS INDICATOR (Continued)

remains illuminated until the cluster receives a sin-
gle lamp-off message from the ACM.
²Actuator Test- Each time the cluster is put
through the actuator test, the airbag indicator will be
turned on, then off again during the bulb check por-
tion of the test to confirm the functionality of the
LED and the cluster control circuitry. The actuator
test illumination of the airbag indicator is a function
of the instrument cluster.
The ACM continually monitors the airbag system
circuits and sensors to decide whether the system is
in good operating condition. The ACM then sends the
proper lamp-on or lamp-off messages to the instru-
ment cluster. If the ACM sends a lamp-on message
after the bulb test, it indicates that the ACM has
detected a system malfunction and/or that the air-
bags and driver seat belt tensioner may not deploy
when required, or may deploy when not required.
The ACM will store a Diagnostic Trouble Code (DTC)
for any malfunction it detects. Each time the airbag
indicator fails to illuminate due to an open or short
in the cluster airbag indicator circuit, the cluster
sends a message notifying the ACM of the condition,
then the instrument cluster and the ACM will each
store a DTC. For proper diagnosis of the airbag sys-
tem, the ACM, the PCI data bus, or the message
inputs to the instrument cluster that control the air-
bag indicator, a DRBIIItscan tool is required. Refer
to the appropriate diagnostic information.
BRAKE/PARK BRAKE
INDICATOR
DESCRIPTION
A brake indicator is standard equipment on all
instrument clusters. The brake indicator is located
near the lower edge of the tachometer dial face in the
instrument cluster. The brake indicator consists of
stencil-like cutouts of the word ªBRAKEº and the
International Control and Display Symbol icon for
ªBrake Failureº 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. A red Light Emitting
Diode (LED) behind the cutout in the opaque layer of
the overlay causes the ªBRAKEº text and the icon to
appear in red through the translucent outer layer of
the overlay when the indicator is illuminated from
behind by the LED, which is soldered onto the
instrument cluster electronic circuit board. The brake
indicator is serviced as a unit with the instrument
cluster.
OPERATION
The brake indicator gives an indication to the vehi-
cle operator when the parking brake is applied, when
there are certain brake hydraulic system malfunc-
tions as indicated by a low brake hydraulic fluid level
condition, or when the brake fluid level switch is dis-
connected. On models equipped with an optional
Antilock Brake System (ABS), the brake indicator
can also give an indication when certain faults are
detected in the ABS. This indicator is controlled by a
transistor on the instrument cluster electronic circuit
board based upon cluster programming, electronic
messages received by the cluster from the Controller
Antilock Brake (CAB) over the Programmable Com-
munications Interface (PCI) data bus (ABS only), and
hard wired inputs from the park brake switch and
the brake fluid level switch. The brake indicator
Light Emitting Diode (LED) 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 LED will always be off when the
ignition switch is in any position except On or Start.
The LED only illuminates when it is provided a path
to ground by the instrument cluster transistor. The
instrument cluster will turn on the brake indicator
for the following reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the brake indicator is illu-
minated by the instrument cluster for about three
seconds as a bulb test.
²Brake Lamp-On Message- Each time the
cluster receives a lamp-on message from the CAB,
the brake indicator will be illuminated. The indicator
remains illuminated until the cluster receives a
lamp-off message from the CAB, or until the ignition
switch is turned to the Off position, whichever occurs
first.
²Park Brake Switch Input- Each time the
cluster detects ground on the park brake switch
sense circuit (park brake switch closed = park brake
applied or not fully released) the brake indicator is
illuminated. The indicator remains illuminated until
the park brake switch sense input to the cluster is an
open circuit (park brake switch open = park brake
fully released), or until the ignition switch is turned
to the Off position, whichever occurs first.
²Brake Fluid Level Switch Input- Each time
the cluster detects ground on the red brake warning
indicator driver circuit (brake fluid level switch
closed = brake hydraulic system fluid level low) the
brake indicator is illuminated solid. The indicator
remains illuminated until the status of the red brake
warning indicator driver input to the cluster is off
(brake fluid level switch off = brake hydraulic system
KJINSTRUMENT CLUSTER 8J - 13
AIRBAG INDICATOR (Continued)

fluid level is not low), or until the ignition switch is
turned to the Off position, whichever occurs first.
²Brake Fluid Level Switch Input Fault- The
brake fluid level switch also features a 1 kilohm
diagnostic resistor connected in parallel between the
switch input and output to provide the cluster with
verification that the red brake warning indicator
driver circuit is not open. If the cluster does not see a
proper input on the red brake warning indicator
driver circuit, it will turn on the brake indicator. The
indicator remains illuminated until the red brake
warning indicator driver circuit fault is resolved, or
until the ignition switch is turned to the Off position,
whichever occurs first.
²Actuator Test- Each time the instrument clus-
ter is put through the actuator test, the brake indi-
cator will be turned on, then off again during the
bulb check portion of the test to confirm the function-
ality of the LED and the cluster control circuitry.
The park brake switch on the park brake pedal
mechanism provides a hard wired ground input to
the instrument cluster circuitry through the park
brake switch sense circuit whenever the park brake
is applied or not fully released. The brake fluid level
switch on the brake master cylinder reservoir pro-
vides a hard wired ground input to the instrument
cluster circuitry through the red brake warning indi-
cator driver circuit whenever the fluid level in the
reservoir becomes low. On models equipped with the
optional ABS, the CAB sends the proper lamp-on or
lamp-off messages to the instrument cluster. If the
CAB sends a lamp-on message after the bulb test, it
indicates that the CAB has detected a brake hydrau-
lic system malfunction and/or that the ABS system
has become inoperative. The CAB will store a Diag-
nostic Trouble Code (DTC) for any malfunction it
detects.
For further diagnosis of the brake indicator or the
instrument cluster circuitry that controls the LED,
(Refer to 8 - ELECTRICAL/INSTRUMENT CLUS-
TER - DIAGNOSIS AND TESTING). The park brake
switch input to the instrument cluster can be diag-
nosed using conventional diagnostic tools and meth-
ods. For proper diagnosis of the brake fluid level
switch input to the instrument cluster, the antilock
brake system, the CAB, the PCI data bus, or the
electronic message inputs to the instrument cluster
that control the brake indicator, a DRBIIItscan tool
is required. Refer to the appropriate diagnostic infor-
mation.
DIAGNOSIS AND TESTING - BRAKE INDICATOR
The diagnosis found here addresses an inoperative
brake indicator condition. If there are problems with
several indicators in the instrument cluster, (Refer to
8 - ELECTRICAL/INSTRUMENT CLUSTER - DIAG-NOSIS AND TESTING). If the brake indicator stays
on with the ignition switch in the On position and
the park brake released, or comes on while driving,
(Refer to 5 - BRAKES - DIAGNOSIS AND TEST-
ING). If no brake system problem is found, the fol-
lowing procedures will help to locate a shorted or
open circuit, or a faulty park brake switch input.
Refer to the appropriate wiring information. The wir-
ing information includes wiring diagrams, proper
wire and connector repair procedures, details of wire
harness routing and retention, connector pin-out
information and location views for the various wire
harness connectors, splices and grounds.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE SUPPLEMENTAL RESTRAINT
SYSTEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, DRIVER AIRBAG,
PASSENGER AIRBAG, SEAT BELT TENSIONER,
FRONT IMPACT SENSORS, SIDE CURTAIN AIRBAG,
OR INSTRUMENT PANEL COMPONENT DIAGNOSIS
OR SERVICE. DISCONNECT AND ISOLATE THE
BATTERY NEGATIVE (GROUND) CABLE, THEN
WAIT TWO MINUTES FOR THE SYSTEM CAPACI-
TOR TO DISCHARGE BEFORE PERFORMING FUR-
THER DIAGNOSIS OR SERVICE. THIS IS THE ONLY
SURE WAY TO DISABLE THE SUPPLEMENTAL
RESTRAINT SYSTEM. FAILURE TO TAKE THE
PROPER PRECAUTIONS COULD RESULT IN ACCI-
DENTAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
INDICATOR ILLUMINATES DURING BULB TEST, BUT DOES
NOT WHEN PARK BRAKE APPLIED
(1) Disconnect and isolate the battery negative
cable. Disconnect the front body wire harness connec-
tor for the park brake switch from the switch termi-
nal. Apply the parking brake. Check for continuity
between the park brake switch terminal and a good
ground. There should be continuity. If OK, go to Step
2. If not OK, replace the faulty park brake switch.
(2) Disconnect the instrument panel wire harness
connector for the instrument cluster from the cluster
connector receptacle. Check for continuity between
the park brake switch sense circuit cavities of the
front body wire harness connector for the park brake
switch and the instrument panel wire harness con-
nector for the instrument cluster. There should be
continuity. If not OK, repair the open park brake
switch sense circuit between the park brake switch
and the instrument cluster as required.
INDICATOR REMAINS ILLUMINATED - BRAKE SYSTEM
CHECKS OK
(1) Disconnect and isolate the battery negative
cable. Disconnect the front body wire harness connec-
8J - 14 INSTRUMENT CLUSTERKJ
BRAKE/PARK BRAKE INDICATOR (Continued)

The BCM continually monitors the door ajar
switches that are integral to each door latch to deter-
mine the status of the doors. The BCM then sends
the proper door ajar lamp-on and lamp-off messages
to the instrument cluster. For further diagnosis of
the door ajar indicator or the instrument cluster cir-
cuitry that controls the indicator, (Refer to 8 - ELEC-
TRICAL/INSTRUMENT CLUSTER - DIAGNOSIS
AND TESTING). For proper diagnosis of the door
ajar switches and circuits, the BCM, the PCI data
bus, or the electronic message inputs to the instru-
ment cluster that control the door ajar indicator, a
DRBIIItscan tool is required. Refer to the appropri-
ate diagnostic information.
ENGINE TEMPERATURE
GAUGE
DESCRIPTION
An engine coolant temperature gauge is standard
equipment on all instrument clusters. The engine
coolant temperature gauge is located in the right
lower corner of the instrument cluster, to the right of
the speedometer. The engine coolant temperature
gauge consists of a movable gauge needle or pointer
controlled by the instrument cluster circuitry and a
fixed 90 degree scale on the cluster overlay that
reads left-to-right from ªCº (or Cold) to ªHº (or Hot)
for all engines. An International Control and Display
Symbol icon for ªEngine Coolant Temperatureº is
located on the cluster overlay, in the center of the
gauge directly above the hub of the gauge needle.
The engine coolant temperature gauge graphics are
dark blue and black against a beige field, except for a
single light blue graduation at the far left (Cold) end
of the gauge scale and a single red graduation at the
far right (Hot) end of the gauge scale, making them
clearly visible within the instrument cluster in day-
light. When illuminated from behind by the panel
lamps dimmer controlled cluster illumination lighting
with the exterior lamps turned On, the blue graphics
appear blue and the red graphics appear red. The
orange gauge needle is internally illuminated. Gauge
illumination is provided by replaceable incandescent
bulb and bulb holder units located on the instrument
cluster electronic circuit board. The engine coolant
temperature gauge is serviced as a unit with the
instrument cluster.
OPERATION
The engine coolant temperature gauge gives an
indication to the vehicle operator of the engine cool-
ant temperature. This gauge is controlled by the
instrument cluster circuit board based upon cluster
programming and electronic messages received bythe cluster from the Powertrain Control Module
(PCM) over the Programmable Communications
Interface (PCI) data bus. The engine coolant temper-
ature 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 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 Temperature Normal Message- Each
time the cluster receives a message from the PCM
indicating the engine coolant temperature is within
the normal operating range [up to about 124É C (255É
F) for gasoline engines, or about 110É C (230É F) for
diesel engines], the gauge needle is moved to the rel-
ative temperature position of the gauge scale.
²Engine Temperature High Message- Each
time the cluster receives a message from the PCM
indicating the engine coolant temperature is high
[above about 127É C (260É F) for gasoline engines, or
112É C (233É F) for diesel engines], the gauge needle
is moved into the center of the red warning zone on
the gauge scale.
²Engine Temperature Critical Message-
Each time the cluster receives a message from the
PCM indicating the engine coolant temperature is
critical [above about 132É C (269É F) for gasoline
engines, or 115É C (239É F) for diesel engines], the
gauge needle is moved to the high end of the red
warning zone on the gauge scale.
²Actuator Test- Each time the cluster is put
through the actuator test, the gauge needle will be
swept to the gauge calibration points on the gauge
scale in sequence in order to confirm the functional-
ity of the gauge and the cluster control circuitry.
The PCM continually monitors the engine coolant
temperature sensor to determine the engine operat-
ing temperature. The PCM then sends the proper
engine coolant temperature messages to the instru-
ment cluster. For further diagnosis of the engine cool-
ant temperature gauge or the instrument cluster
circuitry that controls the gauge, (Refer to 8 - ELEC-
TRICAL/INSTRUMENT CLUSTER - DIAGNOSIS
AND TESTING). If the instrument cluster moves the
engine coolant temperature gauge needle to indicate
a high or critical engine temperature, it may indicate
that the engine or the engine cooling system requires
service. For proper diagnosis of the engine coolant
temperature sensor, the PCM, the PCI data bus, or
the electronic message inputs to the instrument clus-
ter that control the engine coolant temperature
8J - 18 INSTRUMENT CLUSTERKJ
DOOR AJAR INDICATOR (Continued)

three consecutive messages from the PCM indicating
that the engine oil pressure is about 4 kPa or lower
(about 0.6 psi or lower), the low oil pressure indicator
is illuminated. The indicator remains illuminated
until the cluster receives a single message from the
PCM indicating that the engine oil pressure is about
76 kPa or higher (about 11 psi or higher), or until the
ignition switch is turned to the Off position, which-
ever occurs first. Once the cluster monitors and
engine speed of greater than 450 rpm, the cluster
logic will ignore engine speed in determining low oil
pressure indicator operation for the remainder of the
current ignition cycle.
²Actuator Test- Each time the cluster is put
through the actuator test, the low oil pressure indi-
cator will be turned on, then off again during the
bulb check portion of the test to confirm the function-
ality of the LED and the cluster control circuitry.
The PCM continually monitors the engine oil pres-
sure sensor to determine the engine oil pressure. The
PCM then sends the proper engine oil pressure mes-
sages to the instrument cluster. For further diagnosis
of the low oil pressure indicator or the instrument
cluster circuitry that controls the LED, (Refer to 8 -
ELECTRICAL/INSTRUMENT CLUSTER - DIAGNO-
SIS AND TESTING). If the instrument cluster turns
on the indicator after the bulb test, it may indicate
that the engine or the engine oiling system requires
service. For proper diagnosis of the engine oil pres-
sure sensor, the PCM, the PCI data bus, or the elec-
tronic message inputs to the instrument cluster that
control the low oil pressure indicator, a DRBIIItscan
tool is required. Refer to the appropriate diagnostic
information.
MALFUNCTION INDICATOR
LAMP (MIL)
DESCRIPTION
A Malfunction Indicator Lamp (MIL) is standard
equipment on all instrument clusters. The MIL is
located above the coolant temperature gauge and to
the right of the speedometer in the instrument clus-
ter. The MIL consists of a stencil-like cutout of the
International Control and Display Symbol icon for
ªEngineº in the opaque layer of the instrument clus-
ter overlay. The dark outer layer of the overlay pre-
vents the indicator from being clearly visible when it
is not illuminated. An amber Light Emitting Diode
(LED) behind the cutout in the opaque layer of the
overlay causes the icon to appear in amber through
the translucent outer layer of the overlay when it is
illuminated from behind by the LED, which is sol-
dered onto the instrument cluster electronic circuitboard. The MIL is serviced as a unit with the instru-
ment cluster.
OPERATION
The Malfunction Indicator Lamp (MIL) gives an
indication to the vehicle operator when the Power-
train Control Module (PCM) has recorded a Diagnos-
tic Trouble Code (DTC) for an On-Board Diagnostics
II (OBDII) emissions-related circuit or component
malfunction. 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 PCM over the
Programmable Communications Interface (PCI) data
bus. The MIL Light Emitting Diode (LED) is com-
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 LED will
always be off when the ignition switch is in any posi-
tion except On or Start. The LED only illuminates
when it is provided a path to ground by the instru-
ment cluster transistor. The instrument cluster will
turn on the MIL for the following reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the MIL is illuminated for
about seven seconds as a bulb test.
²PCM Lamp-On Message- Each time the clus-
ter receives a malfunction indicator lamp-on message
from the PCM, the indicator will be illuminated. The
indicator can be flashed on and off, or illuminated
solid, as dictated by the PCM message. For some
DTC's, if a problem does not recur, the PCM will
send a lamp-off message automatically. Other DTC's
may require that a fault be repaired and the PCM be
reset before a 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 malfunction indicator lamp-on or lamp-off mes-
sage from the PCM for twenty consecutive seconds,
the MIL is illuminated by the instrument cluster.
The indicator remains controlled and illuminated by
the cluster until a valid malfunction indicator
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,
then off again during the bulb check portion of the
test to confirm the functionality of the LED 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-
8J - 24 INSTRUMENT CLUSTERKJ
LOW OIL PRESSURE INDICATOR (Continued)

On or Start positions, the trip odometer will be reset
to 0.0 kilometers (miles). The VFD must be display-
ing the trip odometer information in order for the
trip odometer information to be reset.
²Warning Display- The odometer or trip odom-
eter information will be toggled at two second inter-
vals with a warning display when certain monitored
conditions are active. If multiple conditions are
active, the VFD will toggle each active warning and
the odometer/trip odometer information at two sec-
ond intervals. Once the vehicle is moving and a vehi-
cle speed input is received by the instrument cluster,
each active warning will be displayed for three two-
second intervals before the VFD reverts to displaying
only the selected odometer or trip odometer informa-
tion. The warnings and monitored conditions include:
²ªdoorº- A door is open or not fully latched.
²ªgateº- The tailgate is open or not fully
latched.
²ªglassº- The rear flip-up glass is open or not
fully latched.
²ªlowashº- The fluid level in the washer reser-
voir is low.
²ªno busº- The instrument cluster can detect no
PCI bus communication. This message is illuminated
solid when there is no PCI bus communication, and
will override the display of all other active warning
displays.
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 the cluster
is unable to display distance information due to an
error internal to the cluster, ªerrorº will be displayed
in the VFD.
²Actuator Test- Each time the cluster is put
through the actuator test, the VFD will step sequen-
tially through a display of ª111111 ºthrough 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 Body Control
Module (BCM), then sends the proper distance mes-
sages to the instrument cluster. For further diagnosis
of the odometer/trip odometer or the instrument clus-
ter circuitry that controls these functions, (Refer to 8
- ELECTRICAL/INSTRUMENT CLUSTER - DIAG-
NOSIS AND TESTING). For proper diagnosis of the
vehicle speed sensor, the BCM, the PCM, the PCI
data bus, or the electronic message inputs to the
instrument cluster that control the odometer/tripodometer, a DRBIIItscan tool is required. Refer to
the appropriate diagnostic information.
OVERDRIVE OFF INDICATOR
DESCRIPTION
An overdrive off indicator is standard equipment
on all instrument clusters, but is only functional on
vehicles equipped with the optional overdrive auto-
matic transmission. The overdrive off indicator is
located above the fuel gauge and to the left of the
tachometer in the instrument cluster. The overdrive
off indicator consists of a stencil-like cutout of the
text ªO/D OFFº in the opaque layer of the instrument
cluster overlay. The dark outer layer of the overlay
prevents the indicator from being clearly visible
when it is not illuminated. An amber Light Emitting
Diode (LED) behind the cutout in the opaque layer of
the overlay causes the ªO/D OFFº text to appear in
amber through the translucent outer layer of the
overlay when it is illuminated from behind by the
LED, which is soldered onto 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 control ring on the left control
stalk of the multi-function switch. The overdrive off
indicator 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 electronic circuit
board based upon the 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
overdrive off indicator Light Emitting Diode (LED) is
completely controlled by the instrument cluster logic
circuit, and that logic will only allow this indicator to
operate when the instrument cluster receives a bat-
tery current input on the fused ignition switch out-
put (run-start) circuit. Therefore, the LED will
always be off when the ignition switch is in any posi-
tion except On or Start. The LED 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:
²Overdrive Off Lamp-On Message- Each time
the cluster receives an overdrive off lamp-on message
8J - 26 INSTRUMENT CLUSTERKJ
ODOMETER (Continued)

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 BCM, 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 5 for diesel engines. The text
ªRPM X 1000º imprinted on the cluster overlay
directly below the hub of the tachometer needle iden-
tifies 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 4300 RPM. The tachometer graphics are
dark blue and red against a beige field, making them
clearly visible within the instrument cluster in day-
light. When illuminated from behind by the panel
lamps dimmer controlled cluster illumination lighting
with the exterior lamps turned On, the dark blue
graphics appear blue and the red graphics appear
red. The orange gauge needle is internally illumi-
nated. Gauge illumination is provided by replaceable
incandescent bulb and bulb holder units located on
the instrument cluster electronic circuit board. 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
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 tomove 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 to several calibration points on the gauge scale
in sequence 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 instrument clusters, but is
only functional on vehicles equipped with an optional
automatic transmission. The transmission over-tem-
perature indicator is located near the lower edge of
the instrument cluster, between the tachometer and
the speedometer. The transmission over-temperature
indicator consists of a stencil-like cutout of the words
ªTRANS TEMPº in the opaque layer of the instru-
ment cluster overlay. The dark outer layer of the
overlay prevents the indicator from being clearly vis-
KJINSTRUMENT CLUSTER 8J - 33
SPEEDOMETER (Continued)

ible when it is not illuminated. An amber Light
Emitting Diode (LED) behind the cutout in the
opaque layer of the overlay causes the ªTRANS
TEMPº text to appear in amber through the translu-
cent outer layer of the overlay when the indicator is
illuminated from behind by the LED, which is sol-
dered onto the instrument cluster electronic circuit
board. The transmission over-temperature indicator
is serviced as a unit with the instrument cluster.
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 the cluster programming and electronic mes-
sages received by the cluster from the Powertrain
Control Module (PCM) over the Programmable Com-
munications Interface (PCI) data bus. The transmis-
sion over-temperature indicator Light Emitting Diode
(LED) 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) circuit. Therefore, the LED
will always be off when the ignition switch is in any
position except On or Start. The LED only illumi-
nates when it is provided a path to ground by the
instrument cluster transistor. The instrument cluster
will turn on the transmission over-temperature indi-
cator 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 Lamp-On Message- Each
time the cluster receives a trans over-temp lamp-on
message from the PCM indicating that the transmis-
sion fluid temperature is 135É C (275É F) or higher,
the indicator will be illuminated. The indicator
remains illuminated until the cluster receives a trans
over-temp lamp-off message from the PCM, 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 trans over-temp indi-
cator will be turned on, then off again during the
bulb check portion of the test to confirm the function-
ality of the LED and the cluster control circuitry.
The PCM continually monitors the transmission
temperature sensor to determine the transmission
operating condition. The PCM then sends the proper
trans over-temp lamp-on and lamp-off messages to
the instrument cluster. If the instrument clusterturns on the transmission over-temperature indicator
due to a high transmission oil temperature condition,
it may indicate that the transmission and/or the
transmission cooling system are being overloaded or
that they require service. For further diagnosis of the
transmission over-temperature 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 transmission temperature
sensor, the PCM, the PCI data bus, or the electronic
message inputs to the instrument cluster that control
the transmission over-temperature indicator, a
DRBIIItscan tool is required. Refer to the appropri-
ate diagnostic information.
TURN SIGNAL INDICATOR
DESCRIPTION
Two turn signal indicators, one right and one left,
are standard equipment on all instrument clusters.
The turn signal indicators are located near the upper
edge of the instrument cluster, between the speedom-
eter and the tachometer. Each turn signal indicator
consists of a stencil-like cutout of the International
Control and Display Symbol icon for ªTurn Warningº
in the opaque layer of the instrument cluster overlay.
The dark outer layer of the overlay prevents these
icons from being clearly visible when they are not
illuminated. A green Light-Emitting Diode (LED)
behind each cutout in the opaque layer of the cluster
overlay causes the indicator to appear in green
through the translucent outer layer of the overlay
when it is illuminated from behind by the LED,
which is soldered onto the instrument cluster elec-
tronic circuit board. The turn signal indicators are
serviced as a unit with the instrument cluster.
OPERATION
The turn signal indicators give an indication to the
vehicle operator that the turn signal (left or right
indicator flashing) or hazard warning (both left and
right indicators flashing) have been selected and are
operating. These indicators are controlled by two
individual hard wired inputs from the combination
flasher circuitry within the hazard switch to the
instrument cluster electronic circuit board. Each turn
signal indicator Light Emitting Diode (LED) is
grounded on the instrument cluster electronic circuit
board at all times; therefore, these indicators remain
functional regardless of the ignition switch position.
Each LED will only illuminate when it is provided
battery current by the combination flasher circuitry
of the hazard switch.
8J - 34 INSTRUMENT CLUSTERKJ
TRANS TEMP INDICATOR (Continued)