2002 JEEP LIBERTY turn signal

²Headlamp Optical Horn- The left (lighting)
control stalk of the multi-function switch is pulled
towards the steering wheel to just before a detent, to
momentarily activate the headlamp optical horn fea-
ture. The high beams will remain illuminated until
the control stalk is released. The multi-function
switch provides a ground output on a high beam
relay control circuit to energize the headlamp high
beam relay (Daytime Running Lamp relay in Cana-
dian vehicles) in the Junction Block (JB) as required.
²Interior Lamps Defeat- The control ring on
the multi-function switch left (lighting) control stalk
is rotated to a full rearward (clockwise) detent to
defeat the illumination of all interior courtesy lamps.
The multi-function switch provides a resistor multi-
plexed output to the Body Control Module (BCM) on
a panel lamps dimmer switch mux circuit, and the
BCM responds by de-energizing its internal courtesy
lamp driver circuit.
²Interior Lamps On- The control ring on the
multi-function switch left (lighting) control stalk is
rotated to a full forward (counterclockwise) detent to
illuminate all interior courtesy lamps. The multi-
function switch provides a resistor multiplexed out-
put to the Body Control Module (BCM) on a panel
lamps dimmer switch mux circuit, and the BCM
responds by energizing its internal courtesy lamp
driver circuit.
²Panel Lamps Dimming- The control ring on
the multi-function switch left (lighting) control stalk
is rotated to one of six minor intermediate detents to
simultaneously select the desired illumination inten-
sity of all adjustable instrument panel and instru-
ment cluster lighting. The control ring is rotated
rearward (clockwise) to dim, or forward (counter-
clockwise) to brighten. The multi-function switch pro-
vides a resistor multiplexed output to the Body
Control Module (BCM) on a panel lamps dimmer
switch mux circuit, and the BCM responds by send-
ing an electronic panel lamps dimming level message
to the ElectroMechanical Instrument Cluster (EMIC)
over the Programmable Communications Interface
(PCI) data bus. The EMIC electronic circuitry then
provides the proper PWM output to the cluster illu-
mination lamps and the VFD on the EMIC circuit
board, then provides a matching PWM output on the
hard wired fused panel lamps dimmer switch signal
circuit.
²Parade Mode- The control ring on the multi-
function switch left (lighting) control stalk is rotated
to an intermediate detent that is one detent rear-
ward (clockwise) from the full forward (counterclock-
wise) detent to select the Parade mode. The multi-
function switch provides a resistor multiplexed
output to the Body Control Module (BCM) on a panel
lamps dimmer switch mux circuit, and the BCMresponds by sending an electronic panel lamps dim-
ming level message to the ElectroMechanical Instru-
ment Cluster (EMIC) over the Programmable
Communications Interface (PCI) data bus. The EMIC
electronic circuitry then provides the proper PWM
output to the cluster illumination lamps and the
VFD on the EMIC circuit board, then provides a
matching PWM output on the hard wired fused panel
lamps dimmer switch signal circuit to illuminate all
lamps at full (daylight) intensity with the exterior
lamps turned On.
²Park Lamps- The control knob on the end of
the multi-function switch left (lighting) control stalk
is rotated forward (counterclockwise) to its first
detent from the Off position to activate the park
lamps. The multi-function switch provides a resistor
multiplexed output to the Body Control Module
(BCM) on a headlamp switch sense circuit, and the
BCM responds by energizing or de-energizing the
park lamp relay in the Junction Block (JB) as
required.
²Rear Fog Lamps- For vehicles so equipped,
the control knob on the end of the multi-function
switch left (lighting) control stalk is rotated forward
(counterclockwise) to its third detent position to acti-
vate the rear fog lamps. The multi-function switch
provides a resistor multiplexed output to the Body
Control Module (BCM) on a headlamp switch sense
circuit, and the BCM responds by energizing or de-
energizing the rear fog lamp relay in the Junction
Block (JB) as required. Rear fog lamps are optional
only for vehicles manufactured for certain markets,
where they are required.
²Turn Signal Control- The left (lighting) con-
trol stalk of the multi-function switch is moved
upward to activate the right turn signal circuitry,
and, downward to activate the left turn signal cir-
cuitry. The turn signal switch has a detent position
in each direction that provides turn signals with
automatic cancellation, and an intermediate, momen-
tary position in each direction that provides turn sig-
nals only until the left multi-function switch control
stalk is released. When the control stalk is moved to
a turn signal switch detent position, the cancel
actuator extends toward the center of the steering
column. A turn signal cancel cam that is integral to
the clockspring rotates with the steering wheel and
the cam lobes contact the cancel actuator when it is
extended from the left multi-function switch. When
the steering wheel is rotated during a turning
maneuver, one of the two turn signal cancel cam
lobes will contact the turn signal cancel actuator. The
cancel actuator latches against the cancel cam rota-
tion in the direction opposite that which is signaled.
In other words, if the left turn signal detent is
selected, the lobes of the cancel cam will ratchet past
KJLAMPS8Ls-49
MULTI-FUNCTION SWITCH (Continued)

the cancel actuator when the steering wheel is
rotated to the left, but will unlatch the cancel actua-
tor as the steering wheel rotates to the right and
returns to center, which will cancel the turn signal
event and release the control stalk from the detent so
it returns to the neutral Off position. When a turn
signal is activated, the multi-function switch provides
a ground output on a right or left turn switch sense
circuit to the combination flasher circuitry within the
hazard switch, and the combination flasher flashes
the turn signal lamps.
RIGHT CONTROL STALK The right (wiper) con-
trol stalk of the multi-function switch operates as fol-
lows:
²Continuous Front Wipe Modes- The control
knob on the end of the multi-function switch right
(wiper) control stalk is rotated to an intermediate
detent that is one detent rearward (counterclockwise)
from the full forward (clockwise) detent to select the
low speed continuous front wiper mode, or to its full
forward (clockwise) detent to select the high speed
continuous front wiper mode. The multi-function
switch provides a resistor multiplexed output to the
Body Control Module (BCM) on a front wiper switch
mux circuit, and the BCM responds by energizing the
wiper on/off relay in the Power Distribution Center
(PDC) for the front low speed continuous wipe mode,
or the wiper on/off relay and the wiper high/low relay
in the PDC for the front high speed continuous wipe
mode as required.
²Continuous Rear Wipe Mode- The control
ring on the multi-function switch right (wiper) con-
trol stalk is rotated to the most forward (clockwise)
detent to select the continuous rear wiper mode. The
multi-function switch provides a battery current out-
put to the rear wiper motor on a rear wiper on driver
circuit to signal the rear wiper motor to operate in
the continuous wipe mode.
²Front Washer Mode- The right (wiper) control
stalk of the multi-function switch is pulled towards
the steering wheel to momentarily activate the
washer pump in the front washer mode. The washer
pump will continue to operate in the front washer
mode until the control stalk is released. The multi-
function switch provides a ground output on a
washer pump sense circuit, and battery current on a
washer pump driver circuit to energize the washer
pump in the front washer mode.
²Front Wiper Mist Mode- The right (wiper)
control stalk of the multi-function switch is pushed
towards the floor to momentarily activate the front
wiper motor in the mist mode. The front wiper motor
will continue to operate in the mist mode until the
control stalk is released. The multi-function switch
provides a resistor multiplexed output to the Body
Control Module (BCM) on a front wiper switch muxcircuit, and the BCM responds by energizing the
wiper on/off relay in the Power Distribution Center
(PDC) to operate the front wiper motor momentarily
at low speed to provide the front wiper mist mode.
²Intermittent Front Wipe Mode- The control
knob on the end of the multi-function switch right
(wiper) control stalk is rotated to one of five minor
intermediate detents to select the desired intermit-
tent front wipe delay interval. The control knob is
rotated rearward (counterclockwise) to increase the
delay, or forward (clockwise) to decrease the delay.
The multi-function switch provides a resistor multi-
plexed output to the Body Control Module (BCM) on
a front wiper switch mux circuit, and the BCM
responds by energizing the wiper on/off relay in the
Power Distribution Center (PDC) to operate the front
wiper motor at the selected delay intervals.
²Intermittent Rear Wipe Mode- The control
ring on the multi-function switch right (wiper) con-
trol stalk is rotated to the center detent to select the
intermittent rear wiper mode. The multi-function
switch provides a battery current output to the rear
wiper motor on a rear wiper intermittent driver cir-
cuit to signal the rear wiper motor to operate in the
intermittent wipe mode.
²Rear Washer Mode- The control ring on the
multi-function switch right (wiper) control stalk is
rotated to either the full forward (clockwise) or full
rearward (counterclockwise) momentary positions to
activate the washer pump in the rear washer mode.
The washer pump will continue to operate in the rear
washer mode until the control ring is released. The
multi-function switch provides a ground output on a
washer pump driver circuit, and battery current on a
washer pump sense circuit to energize the washer
pump in the rear washer mode.
DIAGNOSIS AND TESTING - MULTI-FUNCTION
SWITCH
Refer to the appropriate 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 connectors, splices and grounds.
8Ls - 50 LAMPSKJ
MULTI-FUNCTION SWITCH (Continued)

MULTI-FUNCTION SWITCH TESTS
EXTERIOR LIGHTING FUNCTIONS
SWITCH POSITION CONNECTOR C-1 PINS RESISTANCE (OHMS)  10%
Off 4 & 5 3781
Park Lamps On 4 & 5 911
Headlamp Low Beams On 4 & 5 349
Rear Fog Lamps On 4 & 5 75
Headlamp High Beams On 8 & 9 0 - 1
Front Fog Lamps On 2 & 4 0 - 1
Optical Horn (Flash-to-Pass) On 7 & 8 0 - 1
Turn Signal Neutral 6 & 8,8&10Infinite (Open)
Turn Signal Left 6 & 8 0 - 1
Turn Signal Right 8 & 10 0 - 1
INTERIOR LIGHTING FUNCTIONS
SWITCH POSITION CONNECTOR C-1 PINS RESISTANCE (OHMS)  10%
Off (Courtesy Disable) 1 & 4 63
Dimming 1 1 & 4 200
Dimming 2 1 & 4 557
Dimming 3 1 & 4 914
Dimming 4 1 & 4 1271
Dimming 5 1 & 4 1628
Dimming 6 1 & 4 1985
Parade Mode On 1 & 4 3565
Courtesy On 1 & 4 7885
FRONT WIPER FUNCTIONS
SWITCH POSITIONCONNECTOR C-1 & C-2
PINSRESISTANCE (OHMS)  10%
Front Wiper Off C-1 Pin 4 & C-2 Pin 4 4587
Delay 1 C-1 Pin 4 & C-2 Pin 4 1267
Delay 2 C-1 Pin 4 & C-2 Pin 4 792
Delay 3 C-1 Pin 4 & C-2 Pin 4 531
Delay 4 C-1 Pin 4 & C-2 Pin 4 369
Delay 5 C-1 Pin 4 & C-2 Pin 4 262
Front Wiper Low C-1 Pin 4 & C-2 Pin 4 125
Front Wiper High C-1 Pin 4 & C-2 Pin 4 38
Front Wiper Mist C-1 Pin 4 & C-2 Pin 4 125
Front Washer On C-2 Pins5&7 0-1
REAR WIPER FUNCTIONS
SWITCH POSITION CONNECTOR C-2 PINS RESISTANCE (OHMS)  10%
Rear Wiper Off 1 & 5,2&5Infinite (Open)
Rear Wiper Intermittent 2 & 5 0 - 1
Rear Wiper On 1 & 5 0 - 1
Rear Washer On 2 & 5,3&5 0-1
8Ls - 52 LAMPSKJ
MULTI-FUNCTION SWITCH (Continued)

(4) If the multi-function switch fails any of the
continuity or resistance tests, replace the faulty
switch unit as required.
REMOVAL
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) Disconnect and isolate the battery negative
cable.
(2) If the vehicle is equipped with the optional tilt
steering column, move the tilt steering column to the
fully lowered position and leave the tilt release lever
in the released (down) position.
(3) From below the steering column, remove the
two screws that secure the lower shroud to the upper
shroud (Fig. 52).
(4) Using hand pressure, push gently inward on
both sides of the upper shroud near the parting line
between the upper and lower shrouds to release the
snap features that secure the two halves to each
other.
(5) Remove both the upper and lower shrouds from
the steering column.
(6) Disconnect the two instrument panel wire har-
ness connectors for the multi-function switch from
the two connector receptacles on the back of the
switch housing.
(7) Remove the multi-function switch from the
steering column lock housing by carefully rocking the
switch and pulling the switch housing upward far
enough to disengage its alignment posts and locator
tabs from the lock housing.
INSTALLATION
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.
CAUTION: Before attempting to install the multi-
function switch, be certain that the left control stalk
is in the neutral turn signal position and the turn
signal cancel actuator is in the retracted (neutral)
position.
(1) Position the multi-function switch to the steer-
ing column.
(2) Reconnect the two instrument panel wire har-
ness connectors for the multi-function switch to the
two connector receptacles on the back of the switch
housing (Fig. 52).
Fig. 52 Multi-Function Switch Remove/Install
1 - UPPER SHROUD
2 - MULTI-FUNCTION SWITCH
3 - CLOCKSPRING
4 - LOWER SHROUD
5 - SCREW (2)
6 - STEERING COLUMN
7 - WIRE HARNESS CONNECTOR (2)
KJLAMPS8Ls-53
MULTI-FUNCTION SWITCH (Continued)

TRAILER TOW RELAY
DESCRIPTION
The trailer tow relays are located in a connector
bank above the right rear wheelhouse and behind the
quarter trim panel on vehicles equipped with the
optional factory-installed trailer towing package.
Four individual relays are used, one each for fused
ignition switch output (run), brake lamps, right turn
signal, and left turn signal outputs to a trailer
through the rear body wiring and connectors. The
trailer tow relays are conventional International
Standards Organization (ISO) micro relays (Fig. 64).
Relays conforming to the ISO specifications have
common physical dimensions, current capacities, ter-
minal patterns, and terminal functions. The relay is
contained within a small, rectangular, molded plastic
housing and is connected to all of the required inputs
and outputs by five integral male spade-type termi-
nals that extend from the bottom of the relay base.
The trailer tow relays cannot be adjusted or
repaired and, if faulty or damaged, the inoperative
relay must be replaced.
OPERATION
The trailer tow relays are electromechanical
switches. The relays each use an input from the cir-
cuit that they isolate from the trailer wiring to con-
trol a high current output to the trailer. The movable
common feed contact point is held against the fixed
normally closed contact point by spring pressure.When the relay coil is energized, an electromagnetic
field is produced by the coil windings. This electro-
magnetic field draws the movable relay contact point
away from the fixed normally closed contact point,
and holds it against the fixed normally open contact
point. When the relay coil is de-energized, spring
pressure returns the movable contact point back
against the fixed normally closed contact point. A
resistor is connected in parallel with the relay coil in
the relay, and helps to dissipate voltage spikes and
electromagnetic interference that can be generated as
the electromagnetic field of the relay coil collapses.
The terminals of each trailer tow relay are con-
nected to the vehicle electrical system through a con-
nector bank in the rear lighting wire harness above
the right rear wheelhouse. Refer to the appropriate
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 connectors, splices
and grounds. The trailer tow relays can be diagnosed
using conventional diagnostic tools and methods.
DIAGNOSIS AND TESTING - TRAILER TOW
RELAY
The trailer tow relays (Fig. 65) are located in a
connector bank above the right rear wheelhouse.
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.
Fig. 64 Trailer Tow Relays
1 - RELAY CONNECTOR BANK
2 - REAR BODY WIRE HARNESS
3 - LEFT TURN RELAY
4 - RIGHT TURN RELAY
5 - BRAKE LAMP RELAY
6 - FUSED IGNITION SWITCH OUTPUT (RUN) RELAY
8Ls - 62 LAMPSKJ

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) Position the trailer tow relay to the proper con-
nector in the connector bank (Fig. 67).
(2) Align the trailer tow relay terminals with the
terminal cavities in the connector.
(3) Push firmly and evenly on the top of the trailer
tow relay until the terminals are fully seated in the
terminal cavities in the connector.
(4) Carefully restore the foam wrap around the
trailer tow relay connector bank (Fig. 66).
(5) Reach through the access hole in the quarter
inner panel behind the right rear wheelhouse to
place the trailer tow relay connector bank on the top
of the right rear wheelhouse between the quarter
inner and outer panels.(6) Reinstall the trim onto the right side quarter
inner panel. (Refer to 23 - BODY/INTERIOR/QUAR-
TER TRIM PANEL - INSTALLATION).
(7) Reconnect the battery negative cable.
TRAILER TOW WIRING
DESCRIPTION
Vehicles equipped with an optional factory-in-
stalled (not dealer-installed or port-installed) trailer
towing package have a rear body wire harness that
includes an integral trailer tow wiring take out that
connects to a heavy duty, sealed, 7-pin trailer tow
connector located on a bracket on the trailer hitch
receiver (Fig. 68). This harness includes a second
take out with a trailer tow relay connector bank and
four trailer tow relays that isolate the right turn sig-
nal, left turn signal, and brake lamp circuits of the
vehicle from the electrical system of the trailer. The
fourth relay in the connector bank provides a fused
ignition switch output (run) source of battery current
to the trailer tow connector through a trailer tow
relay output circuit. The package also includes an
adapter harness (stored beneath the left rear seat
cushion of the vehicle when it is shipped from the
factory) that adapts the 7-pin trailer tow connector to
a standard, light-duty, 4-pin trailer tow connector.
Refer to the appropriate wiring information. The wir-
ing information includes wiring diagrams, proper
wire and connector repair procedures, further details
on wire harness routing and retention, as well as
pin-out and location views for the various wire har-
ness connectors, splices and grounds.
Fig. 67 Trailer Tow Relay Remove/Install
1 - RELAY CONNECTOR BANK
2 - REAR BODY WIRE HARNESS
3 - LEFT TURN RELAY
4 - RIGHT TURN RELAY
5 - BRAKE LAMP RELAY
6 - FUSED IGNITION SWITCH OUTPUT (RUN) RELAY
Fig. 68 Trailer Tow Wiring
1 - RETAINER CLIP (4)
2 - REAR BODY HARNESS (TRAILER TOW TAKE OUT)
3 - RETAINER CLIP (2)
4 - WIRE HARNESS CONNECTOR
8Ls - 64 LAMPSKJ
TRAILER TOW RELAY (Continued)

NOTE: Individual channels cannot be erased. Eras-
ing the transmitter codes will erase ALL pro-
grammed codes.
STANDARD PROCEDURE - SETTING
TRANSMITTER CODES
(1) Turn off the engine.
(2) Erase the factory test codes by pressing but-
tons 1 and 3. Release the buttons when the two
green lights begin to flash (about 20 seconds).
(3) Choose one of the three buttons to train. Place
the hand-held transmitter within one inch of the uni-
versal transmitter and push the buttons on both
transmitters. The green dot below the house symbol
will begin to flash slowly.
(4) When the red light on the universal transmit-
ter begins to flash rapidly (this may take as long as
60 seconds), release both buttons. Your universal
transmitter is now ªtrainedº. To train the other but-
tons, repeat Step 3 and Step 4. Be sure to keep your
hand-held transmitter in case you need to retrain the
universal transmitter.
AMBIENT TEMP SENSOR
DESCRIPTION
Ambient air temperature is monitored by the Com-
pass Mini-Trip Computer (CMTC) through ambient
temperature sensor messages received from the Body
Control Module (BCM) over the Programmable Com-
munications Interface (PCI) data bus network. The
BCM receives a hard wired input from the ambient
temperature sensor. The ambient temperature sensor
(Fig. 8) is a variable resistor mounted in front the
radiator, behind the grille, near the center of the
vehicle.
Refer toBody Control Modulein Electronic Con-
trol Modules. For complete circuit diagrams, refer to
the appropriate wiring information. The ambient
temperature sensor cannot be adjusted or repaired
and, if faulty or damaged, it must be replaced.
OPERATION
The ambient temperature sensor is a variable
resistor that operates on a five-volt reference signal
sent to it by the BCM. The resistance in the sensor
changes as temperature changes, changing the tem-
perature sensor signal circuit voltage to the BCM.
Based upon the resistance in the sensor, the BCM
senses a specific voltage on the temperature sensor
signal circuit, which it is programmed to correspond
to a specific temperature. The BCM then sends the
proper ambient temperature messages to the CMTC
over the PCI data bus.
The thermometer function is supported by the
ambient temperature sensor, a wiring circuit, the
Body Control Module (BCM), the Programmable
Communications Interface (PCI) data bus, and a por-
tion of the Compass Mini-Trip Computer module.
The ambient temperature sensor circuit can also be
diagnosed by referring toDiagnosis and Testing -
Ambient Temperature Sensor, and Diagnosis
and Testing - Ambient Temperature Sensor Cir-
cuit. If the temperature sensor and circuit are con-
firmed to be OK, but the temperature display is
inoperative or incorrect, refer toDiagnosis and
Testing - Compass Mini-Trip Computerin this
section. For complete circuit diagrams, refer to the
appropriate wiring information.
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - AMBIENT
TEMPERATURE SENSOR
(1) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Disconnect the ambient temperature sensor wire har-
ness connector.
(2) Measure the resistance of the ambient temper-
ature sensor. At ±40É C (±40É F), the sensor resis-
tance is 336 kilohms. At 55É C (140É F), the sensor
resistance is 2.488 kilohms. The sensor resistance
should read between these two values. If OK, refer to
Diagnosis and Testing - Ambient Temperature
Sensor Circuitin this group. If not OK, replace the
faulty ambient temperature sensor.
DIAGNOSIS AND TESTING - AMBIENT
TEMPERATURE SENSOR CIRCUIT
(1) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Disconnect the ambient temperature sensor wire har-
ness connector and the Body Control Module wire
harness connector.
(2) Connect a jumper wire between the two termi-
nals in the body half of the ambient temperature sen-
sor wire harness connector.
Fig. 8 Ambient Temperature Sensor
KJMESSAGE SYSTEMS 8M - 9
UNIVERSAL TRANSMITTER (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)