2002 JEEP LIBERTY cavity

HORN SWITCH
DESCRIPTION
The horn switch is molded into the driver airbag
assembly. The horn switch can not be serviced sepa-
rately. For service procedures, (Refer to 8 - ELEC-
TRICAL/RESTRAINTS/DRIVER AIRBAG -
REMOVAL).
DIAGNOSIS AND TESTING - HORN SWITCH
For complete circuit diagrams, refer to the appro-
priate wiring information. The wiring information
includes wiring diagrams, proper wire and connector
repair procedures, details of wire harness routing
and retention, connector pin-out information and
location views for the various wire harness connec-
tors, splices and grounds.
WARNING: DISABLE THE AIRBAG SYSTEM
BEFORE ATTEMPTING ANY STEERING WHEEL,
STEERING COLUMN, SEAT BELT TENSIONER, SIDE
AIRBAG, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the steering column opening cover.
(3) Check for continuity between the metal steer-
ing column jacket and a good ground. There should
be continuity. If OK, go to Step 4. If not OK,(Refer to
19 - STEERING/COLUMN - INSTALLATION) for
proper installation of the steering column.
(4) Remove the driver side airbag module from the
steering wheel (Refer to 8 - ELECTRICAL/RE-
STRAINTS/DRIVER AIRBAG - REMOVAL). Discon-
nect the horn switch wire harness connectors from
the driver side airbag module (Fig. 4).
(5) Remove the horn relay from the Junction Block
(JB). Check for continuity between the steering col-umn half of the horn switch feed wire harness con-
nector and a good ground. There should be no
continuity. If OK, go to Step 6. If not OK, repair the
shorted horn relay control circuit to the horn relay in
the Junction Block as required.
(6) Check for continuity between the steering col-
umn half of the horn switch feed wire harness con-
nector and the horn relay control circuit cavity for
the horn relay in the Junction Block. There should be
continuity. If OK, go to Step 7. If not OK, repair the
open horn relay control circuit to the horn relay in
the Junction Block as required.
(7) Check for continuity between the horn switch
feed wire and the horn switch ground wire on the
driver side airbag module. There should be no conti-
nuity. If OK, go to Step 8. If not OK, replace the
faulty horn switch.
(8) Depress the center of the driver side airbag
module trim cover and check for continuity between
the horn switch feed wire and the horn switch
ground wire on the driver side airbag module. There
should now be continuity. If not OK, replace the
faulty horn switch (Refer to 8 - ELECTRICAL/RE-
STRAINTS/DRIVER AIRBAG - REMOVAL).
Fig. 4 Driver Airbag Housing
1 - HOUSING
2 - HORN SWITCH GROUND WIRE
3 - HORN SWITCH FEED WIRE
4 - INFLATOR
5 - TRIM COVER
8H - 4 HORNKJ

fused panel lamps dimmer switch signal circuit. The
cluster illumination lamps are grounded at all times.
In addition, the control ring on the left (lighting)
control stalk of the multi-function switch has a
Parade Mode position to provide a parade mode. The
BCM monitors the request for this mode from the
multi-function switch, then sends an electronic dim-
ming level message to the EMIC over the PCI data
bus to illuminate all VFDs in the vehicle at full
intensity for easier visibility when driving in daylight
with the exterior lighting turned On.
The hard wired cluster illumination lamp circuits
may be diagnosed using conventional diagnostic
methods. However, proper testing of the PWM output
of the EMIC and the electronic dimming level mes-
sages sent by the BCM over the PCI data bus
requires the use of a DRBIIItscan tool. Refer to the
appropriate diagnostic information.
CHIME WARNING SERVICE The EMIC is pro-
grammed to provide chime service when certain indi-
cators are illuminated. When the programmed
conditions are met, the EMIC generates an electronic
chime tone through its integral chime tone generator.
In addition, the EMIC is programmed to provide
chime service for other electronic modules in the
vehicle when it receives the proper electronic chime
request messages over the PCI data bus. Upon
receiving the proper chime request message, the
EMIC activates the integral chime tone generator to
provide the audible chime tone to the vehicle opera-
tor. (Refer to 8 - ELECTRICAL/CHIME/BUZZER -
OPERATION). Proper testing of the EMIC and the
PCI data bus chime request message functions
requires the use of a DRBIIItscan tool. Refer to the
appropriate diagnostic information.
DIAGNOSIS AND TESTING - INSTRUMENT
CLUSTER
If all of the instrument cluster gauges and/or indi-
cators are inoperative, refer to PRELIMINARY
DIAGNOSIS . If an individual gauge or Programma-
ble Communications Interface (PCI) data bus mes-
sage-controlled indicator is inoperative, refer to
ACTUATOR TEST . If an individual hard wired indi-
cator is inoperative, refer to the diagnosis and testing
information for that specific indicator. If the instru-
ment cluster chime service is inoperative, refer to
CHIME SERVICE DIAGNOSIS . If the instrument
cluster illumination lighting is inoperative, refer to
CLUSTER ILLUMINATION DIAGNOSIS . Refer to
the appropriate wiring information. The wiring infor-
mation 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 con-
nectors, splices and grounds.NOTE: Certain indicators in this instrument cluster
are automatically configured. This feature allows
those indicators to be activated for compatibility
with certain optional equipment. If the problem
being diagnosed involves illumination of the ABS
indicator, the airbag indicator, or the SKIS indicator
when the vehicle does not have this equipment, a
DRBIIITscan tool must be used to disable the erro-
neous indicator(s). Refer to the appropriate diag-
nostic information.
PRELIMINARY DIAGNOSIS
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE SUPPLEMENTAL RESTRAINT
SYSTEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, DRIVER AIRBAG,
PASSENGER AIRBAG, 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.
(1) Check the fused B(+) fuse (Fuse 34 - 15
ampere) in the Junction Block (JB). If OK, go to Step
2. If not OK, repair the shorted circuit or component
as required and replace the faulty fuse.
(2) Check for battery voltage at the fused B(+) fuse
(Fuse 34 - 15 ampere) in the JB. If OK, go to Step 3.
If not OK, repair the open fused B(+) circuit between
the JB and the Power Distribution Center (PDC) as
required.
(3) Disconnect and isolate the battery negative
cable. Remove the instrument cluster. Reconnect the
battery negative cable. Check for battery voltage at
the fused B(+) circuit cavity of the instrument panel
wire harness connector for the instrument cluster. If
OK, go to Step 4. If not OK, repair the open fused
B(+) circuit between the instrument cluster and the
JB as required.
(4) Check the fused ignition switch output (run-
start) fuse (Fuse 13 - 10 ampere) in the JB. If OK, go
to Step 5. If not OK, repair the shorted circuit or
component as required and replace the faulty fuse.
(5) Turn the ignition switch to the On position.
Check for battery voltage at the fused ignition switch
output (run-start) fuse (Fuse 13 - 10 ampere) in the
JB. If OK, go to Step 6. If not OK, repair the open
KJINSTRUMENT CLUSTER 8J - 7
INSTRUMENT CLUSTER (Continued)

fused ignition switch output (run-start) circuit
between the JB and the ignition switch as required.
(6) With the ignition switch still in the On posi-
tion, check for battery voltage at the fused ignition
switch output (run-start) circuit cavity of the instru-
ment panel wire harness connector for the instru-
ment cluster. If OK, go to Step 7. If not OK, repair
the open fused ignition switch output circuit (run-
start) between the instrument cluster and the JB as
required.
(7) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Check for continuity between the ground circuit cav-
ity of the instrument panel wire harness connector
for the instrument cluster and a good ground. There
should be continuity. If OK, refer to ACTUATOR
TEST . If not OK, repair the open ground circuit
between the instrument cluster and ground (G202) as
required.
ACTUATOR TEST
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.
The instrument cluster actuator test will put the
instrument cluster into its self-diagnostic mode. In
this mode the instrument cluster can perform a self-
diagnostic test that will confirm that the instrument
cluster circuitry, the gauges, the PCI data bus mes-
sage controlled indicator lamps, and the chime tone
generator are capable of operating as designed. Dur-
ing the actuator test the instrument cluster circuitry
will sound the chime tone generator, position each of
the gauge needles at various specified calibration
points, illuminate each of the segments in the Vacu-um-Fluorescent Display (VFD), and turn all of the
PCI data bus message-controlled indicators on and
off again.
Successful completion of the actuator test will con-
firm that the instrument cluster is operational. How-
ever, there may still be a problem with the PCI data
bus, the Powertrain Control Module (PCM), the Air-
bag Control Module (ACM), the Sentry Key Immobi-
lizer Module (SKIM), or the inputs to one of these
electronic control modules. Use a DRBIIItscan tool
to diagnose these components. Refer to the appropri-
ate diagnostic information.
(1) Begin the test with the ignition switch in the
Off position.
(2) Depress the odometer/trip odometer switch but-
ton.
(3) While still holding the odometer/trip odometer
switch button depressed, turn the ignition switch to
the On position, but do not start the engine.
(4) Release the odometer/trip odometer switch but-
ton.
(5) The instrument cluster will automatically
begin the actuator test sequence, as follows:
(a) The cluster will turn on, then off again each
of the PCI data bus message controlled indicators
to confirm the functionality of the indicator and
the cluster control circuitry:
(b) The cluster will sweep the needles for each of
the gauges to several calibration points in sequence
to confirm the functionality of the gauge and the
cluster control circuitry:
(c) The cluster will sequentially step the odome-
ter/trip odometer VFD display from all ones
( 111111 )through all nines (999999) to confirm the
functionality of all VFD segments and their control
circuitry, then display the software version number.
(d) The cluster will generate five (5) chime tones
to confirm the functionality of the chime tone gen-
erator and the chime control circuitry.
(6) The actuator test is now completed. The instru-
ment cluster will automatically exit the self-diagnos-
tic mode and return to normal operation at the
completion of the test, if the ignition switch is turned
to the Off position during the test, or if an engine
rpm message indicating that the engine is running is
received from the PCM over the PCI data bus during
the test.
(7) Go back to Step 1 to repeat the test, if
required.
8J - 8 INSTRUMENT CLUSTERKJ
INSTRUMENT CLUSTER (Continued)

tor for the park brake switch from the switch termi-
nal. Check for continuity between the terminal of the
park brake switch and a good ground. There should
be no continuity with the park brake released, and
continuity with the park brake applied. 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 cavity of the front
body wire harness connector for the park brake
switch and a good ground. There should be no conti-
nuity. If not OK, repair the shorted park brake
switch sense circuit between the park brake switch
and the instrument cluster as required.
CHARGING INDICATOR
DESCRIPTION
A charging indicator is standard equipment on all
instrument clusters. The charging indicator is located
above the engine temperature gauge and to the right
of the speedometer in the instrument cluster. The
charging indicator consists of a stencil-like cutout of
the International Control and Display Symbol icon
for ªBattery Charging Conditionº 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. A red Light
Emitting Diode (LED) behind the cutout in the
opaque layer of the overlay causes 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
charging indicator is serviced as a unit with the
instrument cluster.
OPERATION
The charging indicator gives an indication to the
vehicle operator when the electrical system voltage is
too low or too high. 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
charging 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 charging indicator for the following rea-
sons:
²Bulb Test- Each time the ignition switch is
turned to the On position the charging indicator is
illuminated by the instrument cluster for about three
seconds as a bulb test.
²Charge Fail Message- Each time the cluster
receives a charge fail message from the PCM (system
voltage is nine volts or lower, the charging indicator
will be illuminated. The indicator remains illumi-
nated until the cluster receives a message from the
PCM indicating there is no charge fail condition (sys-
tem voltage is twelve volts or higher, but lower than
sixteen volts), or until the ignition switch is turned to
the Off position, whichever occurs first.
²Voltage High Message- Each time the cluster
receives a message from the PCM indicating a volt-
age high condition (system voltage is sixteen volts or
higher), the lamp will be illuminated. The lamp
remains illuminated until the cluster receives a mes-
sage from the PCM indicating there is no voltage
high condition (system voltage is lower than sixteen
volts, but higher than nine volts), or until the igni-
tion switch is turned to the Off position, whichever
occurs first.
²Actuator Test- Each time the cluster is put
through the actuator test, the charging indicator 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 the electrical sys-
tem voltage to control the generator output. The
PCM then sends the proper system voltage messages
to the instrument cluster. If the instrument cluster
turns on the indicator after the bulb test, it may
indicate that the charging system requires service.
For further diagnosis of the charging 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 charging system, the PCI
data bus, or the electronic message inputs to the
instrument cluster that control the charging indica-
tor, a DRBIIItscan tool is required. Refer to the
appropriate diagnostic information.
COOLANT LOW INDICATOR
DESCRIPTION
A coolant low indicator is only found in the instru-
ment clusters of vehicles equipped with an optional
diesel engine. The coolant low indicator is located
KJINSTRUMENT CLUSTER 8J - 15
BRAKE/PARK BRAKE INDICATOR (Continued)

ity of the headlamp and dash wire harness connector
for the washer fluid level switch and a good ground.
There should be continuity. If OK, go to Step 2. If not
OK, repair the open ground circuit to ground (G111)
as required.
(2) Remove the instrument cluster from the instru-
ment panel. Check for continuity between the washer
fluid sense circuit cavities of the headlamp and dash
wire harness connector for the washer fluid level
switch and the instrument panel wire harness con-
nector (Connector C2) for the instrument cluster. If
OK, replace the faulty washer fluid level switch. If
not OK, repair the open washer fluid switch sense
circuit between the washer fluid level switch and the
instrument cluster as required.
INDICATOR STAYS ILLUMINATED WITH WASHER
RESERVOIR FULL
(1) Disconnect and isolate the battery negative
cable. Disconnect the headlamp and dash wire har-
ness connector for the washer fluid level switch from
the washer fluid level switch connector receptacle.
Check for continuity between the ground circuit ter-
minal and the washer fluid sense terminal in the
washer fluid level switch connector receptacle. There
should be no continuity. If OK, go to Step 2. If not
OK, replace the faulty washer fluid level switch.
(2) Remove the instrument cluster from the instru-
ment panel. Check for continuity between the washer
fluid sense circuit cavity of the headlamp and dash
wire harness connector for the washer fluid level
switch and a good ground. There should be no conti-
nuity. If not OK, repair the shorted washer fluid
switch sense circuit between the washer fluid level
switch and the instrument cluster as required.
WATER-IN-FUEL INDICATOR
DESCRIPTION
A water-in-fuel indicator is only found in the
instrument clusters of vehicles equipped with an
optional diesel engine. The water-in-fuel indicator is
located above the coolant temperature gauge and to
the right of the speedometer in the instrument clus-
ter. The water-in-fuel indicator consists of a stencil-
like cutout of the International Control and Display
Symbol icon for ªWater In Fuelº 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. A red Light
Emitting Diode (LED) behind the cutout in the
opaque layer of the overlay causes 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. Thewater-in-fuel indicator is serviced as a unit with the
instrument cluster.
OPERATION
The water-in-fuel indicator gives an indication to
the vehicle operator when there is excessive water in
the fuel system. This indicator is controlled by a
transistor on 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
water-in-fuel 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 water-in-fuel indicator for the following
reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the water-in-fuel indicator
is illuminated for about three seconds as a bulb test.
²Water-In-Fuel Lamp-On Message- Each time
the cluster receives a water-in-fuel lamp-on message
from the PCM indicating there is excessive water in
the diesel fuel system, the water-in-fuel indicator will
be illuminated. The indicator remains illuminated
until the cluster receives a water-in-fuel 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 water-in-fuel indicator
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 the water-in-fuel
sensor to determine whether there is excessive water
in the diesel fuel. The PCM then sends the proper
water-in-fuel lamp-on and lamp-off messages to the
instrument cluster. For further diagnosis of the
water-in-fuel 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 water-
in-fuel-sensor, the PCM, the PCI data bus, or the
electronic message inputs to the instrument cluster
that control the water-in-fuel indicator, a DRBIIIt
scan tool is required. Refer to the appropriate diag-
nostic information.
KJINSTRUMENT CLUSTER 8J - 37
WASHER FLUID INDICATOR (Continued)

²STEP
²C/T - Compass/Temperature
²US/M - English/Metric
²RESET
1. STEP BUTTON
Pressing the STEP button selects one of the follow-
ing 6 displays:
²Average fuel economy
²Distance to empty
²Instantaneous fuel economy
²Trip odometer
²Elapsed time
²Blank Screen
2. C/T (COMPASS/TEMPERATURE)
BUTTON
Pressing the C/T button selects the Compass/Tem-
perature display.
3. US/M (ENGLISH/METRIC
MEASUREMENT) BUTTON
Pressing the US/M button switches the display
units between English and Metric readings.
4. RESET BUTTON
Pressing the RESET button resets the function on
the display, provided that function can be reset. The
functions which can be reset are Average fuel econ-
omy, Trip odometer and Elapsed time.
Global ResetThis feature allows all three dis-
plays (Average fuel economy, Trip odometer and
Elapsed time) to be reset easily, by pressing the
RESET button twice within three seconds with any
of the screens in display. This eliminates the need to
reset each display individually.
The RESET button is also used to set the variance
and/or calibrate the compass. Refer to the Variance
Procedure and Calibration Procedure in this section.
For more information on the features, control func-
tions and setting procedures for the CMTC module,
see the owner's manual in the vehicle glove box.
DIAGNOSIS AND TESTING - COMPASS
MINI-TRIP COMPUTER
The following diagnostic procedure can be used if
the compass mini-trip computer is not operational in
any way. If the problem is specific to a individual
CMTC display, go to the appropriate display title
noted below and diagnose using the information pro-
vided on how these displays are generated.
(1) Remove the overhead console from the head-
liner (Refer to 8 - ELECTRICAL/OVERHEAD CON-
SOLE - REMOVAL).
(2) Using a ohmmeter, check the ground circuit
cavity of the compass mini-trip computer electricalconnector for proper continuity to ground. Continuity
should be present, If OK go to Step 3, If not OK
repair the open or shorted ground circuit as required.
NOTE: Connect the negative battery cable before
proceeding.
(3) Using a voltmeter, check the fused (B+) circuit
cavity of the compass mini-trip computer electrical
connector for 12v. Voltage should be present, If OK go
to Step 4, If not OK repair the open or shorted fused
(B+) circuit as required.
(4) Using a voltmeter, check the fused ignition
switch output circuit cavity of the compass mini-trip
computer electrical connector for 12v with Key ON.
Voltage should be present, If OK, replace the inoper-
ative CMTC module, If not OK repair the open or
shorted fused ignition switch output circuit as
required.
TEMPERATURE
The compass mini-trip computer receives Program-
mable Communications Interface bus (PCI bus) mes-
sages from the Body Control Module (BCM) for all
displayed information except the compass display. If
a dash (-) is displayed, the compass mini-trip com-
puter is not receiving a PCI bus message from the
BCM. To check out the PCI bus line and the BCM,
use the DRB llltscan tool and proper Body Diagnos-
tic Procedure Manual.
If the compass mini-trip computer displays a tem-
perature more than 54É C (130É F), check for a short
circuit between the temperature sensor and the
BCM.
If the compass mini-trip computer displays a tem-
perature less than -40É C (-67É F), check for an open
circuit between the temperature sensor and the
BCM.
AVERAGE FUEL ECONOMY
The compass mini-trip computer receives average
fuel economy information from the BCM over the PCI
bus line. If the compass mini-trip computer displays
-.- instead of an average fuel economy value, it is not
receiving a PCI bus message for the average fuel
economy from the BCM. To check out the PCI bus
line and the BCM use the DRB llltscan tool and
proper Body Diagnostic Procedure Manual.
DISTANCE TO EMPTY
The compass mini-trip computer receives distance
to empty information from the BCM over the PCI bus
line. If compass mini-trip computer displays a dash
(-) instead of a distance to empty value, it is not
receiving a PCI bus message for the distance to
empty from the BCM. To check out the PCI bus line
8M - 6 MESSAGE SYSTEMSKJ
COMPASS/MINI-TRIP COMPUTER (Continued)

(3) Check for continuity between the sensor return
circuit and the ambient temperature sensor signal
circuit cavities of the BCM wire harness connector.
There should be continuity. If OK, go to Step 4. If not
OK, repair the open sensor return circuit or ambient
temperature sensor signal circuit to the ambient tem-
perature sensor as required.
(4) Remove the jumper wire from the body half of
the ambient temperature sensor wire harness con-
nector. Check for continuity between the sensor
return circuit cavity of the BCM wire harness con-
nector and a good ground. There should be no conti-
nuity. If OK, go to Step 5. If not OK, repair the
shorted sensor return circuit as required.
(5) Check for continuity between the ambient tem-
perature sensor signal circuit cavity of the BCM wire
harness connector and a good ground. There should
be no continuity. If OK, refer toDiagnosis and
Testing - Compass Mini-Trip Computerin this
group. If not OK, repair the shorted ambient temper-
ature sensor signal circuit as required.REMOVAL
(1) Open hood, disconnect and isolate the negative
battery cable.
(2) Remove the grille from the vehicle (Refer to 23
- BODY/EXTERIOR/GRILLE - REMOVAL).
(3) Disconnect the ambient temperature sensor
electrical connector.
(4) Remove the ambient temperature sensor
retaining screw and remove the sensor from the vehi-
cle.
INSTALLATION
(1) Position the ambient temperature sensor and
install the retaining screw.
(2) Connect the ambient temperature sensor elec-
trical connector.
(3) Install the grille on the vehicle (Refer to 23 -
BODY/EXTERIOR/GRILLE - INSTALLATION).
(4) Connect the negative battery cable.
8M - 10 MESSAGE SYSTEMSKJ
AMBIENT TEMP SENSOR (Continued)

FRONT IMPACT SENSOR
DESCRIPTION
Two front impact sensors are used on this model,
one each for the left and right sides of the vehicle
(Fig. 17). These sensors are mounted remotely from
the impact sensor that is internal to the Airbag Con-
trol Module (ACM). Each front sensor is secured with
two screws to the backs of the right and left vertical
members of the radiator support within the engine
compartment. The sensor housing has an integral
connector receptacle and two integral mounting
points each with a metal sleeve to provide crush pro-
tection.
The right and left front impact sensors are identi-
cal in construction and calibration with two excep-
tions:
²On models equipped with an optional 2.4L gaso-
line engine, the left front impact sensor includes a
shim that moves the sensor three millimeters toward
the rear of the vehicle on the left vertical member of
the radiator support for additional clearance that is
required for that application.
²On models equipped with an optional diesel
engine, the left front impact sensor includes a
stamped metal mounting bracket that rotates theconnector receptacle end of the sensor toward the
outboard side of the vehicle for additional clearance
that is required for that application.
A cavity in the center of the molded black plastic
impact sensor housing contains the electronic cir-
cuitry of the sensor which includes an electronic com-
munication chip and an electronic impact sensor.
Potting material fills the cavity to seal and protect
the internal electronic circuitry and components. The
front impact sensors are each connected to the vehi-
cle electrical system through a dedicated take out
and connector of the headlamp and dash wire har-
ness.
The impact sensors cannot be repaired or adjusted
and, if damaged or faulty, they must be replaced. The
mounting bracket for the left front impact sensor on
models with a diesel engine is serviced as a unit with
that sensor.
OPERATION
The front impact sensors are electronic accelerom-
eters that sense the rate of vehicle deceleration,
which provides verification of the direction and sever-
ity of an impact. Each sensor also contains an elec-
tronic communication chip that allows the unit to
communicate the sensor status as well as sensor
fault information to the microprocessor in the Airbag
Control Module (ACM). The ACM microprocessor con-
tinuously monitors all of the front passive restraint
system electrical circuits to determine the system
readiness. If the ACM detects a monitored system
fault, it sets a Diagnostic Trouble Code (DTC) and
controls the airbag indicator operation accordingly.
The impact sensors each receive battery current and
ground through dedicated left and right sensor plus and
minus circuits from the ACM. The impact sensors and
the ACM communicate by modulating the voltage in the
sensor plus circuit. The hard wired circuits between the
front impact sensors and the ACM may be diagnosed
and tested using conventional diagnostic tools and pro-
cedures. However, conventional diagnostic methods will
not prove conclusive in the diagnosis of the ACM or the
impact sensors. The most reliable, efficient, and accu-
rate means to diagnose the impact sensors, the ACM,
and the electronic message communication between the
sensors and the ACM requires the use of a DRBIIIt
scan tool. Refer to the appropriate diagnostic informa-
tion.
Fig. 17 Front Impact Sensor
1 - SENSOR
2 - CONNECTOR RECEPTACLE
KJRESTRAINTS 8O - 21