2002 CHRYSLER VOYAGER Electronic Control Modules

(2) Install and tighten the three screws that secure
the heated seat switch to the back of the instrument
panel center bezel. Tighten the screws to 1.5 N´m (13
in. lbs.) (Fig. 4).
(3) Install the center bezel onto the instrument
panel. Refer toInstrument Panel Center Bezelin
the Body section for the procedure.
(4) Reconnect the battery negative cable.
HEATED SEAT ELEMENT
DESCRIPTION
The heated seat system includes two seat heating ele-
ments in each front seat, one for the seat cushion and
the other for the seat back. The two elements for each
seat that are connected in series with the Heated Seat
Module (HSM). The temperature sensor is a Negative
Temperature Coefficient (NTC) thermistor. One temper-
ature sensor is used for each seat, and it is located on
the seat cushion heating element for all models.
The seat heating elements are sewn into the seat
cushion cover trim and seat back cover trim units.
The heated seat elements and the temperature sen-
sor cannot be adjusted or repaired and, if faulty or
damaged, the seat element assembly must be
replaced. Refer to the procedure in this section.
OPERATION
The heated seat elements resist the flow of electrical
current. When battery current is passed through the
elements, the energy lost by the resistance of the ele-
ments to the current flow is released in the form of
heat. The temperature sensor is a NTC thermistor.
When the temperature of the seat cushion cover rises,
the resistance of the sensor decreases. The heated seat
module supplies a five-volt current to one side of each
sensor, and monitors the voltage drop through the
sensor on a return circuit. The heated seat module
uses this temperature sensor input to monitor the
temperature of the seat, and regulates the current
flow to the seat heating elements accordingly.
DIAGNOSIS AND TESTING - HEATED SEAT
ELEMENTS
The wire harness connectors for the seat cushion and
seat back heating elements are located under the seat,
at the heated seat module. For circuit descriptions and
diagrams, refer to section 8W, Wiring Diagrams.
In order to access and test the heated seat ele-
ments it will be necessary to remove the appropriate
front seat retaining bolts and lay the seat rearward,
up against one of the rear seats. It is not necessary
to disconnect the seat electrical connectors, just use
care not to damage the attached wire harnesses
while testing.NOTE: WHEN CHECKING HEATED SEAT ELE-
MENTS FOR CONTINUITY, BE CERTAIN TO MOVE
THE HEATING ELEMENT BEING CHECKED. MOV-
ING THE ELEMENT, SUCH AS SITTING IN THE SEAT
WILL ELIMINATE THE POSSIBILITY OF AN INTER-
MITTENT OPEN IN THE ELEMENT WHICH WOULD
ONLY BE EVIDENT IF THE ELEMENT WAS MOVED
IN A CERTAIN DIRECTION. FAILURE TO CHECK
THE ELEMENT IN VARIOUS POSITIONS COULD
RESULT IN AN INCOMPLETE TEST.
SEAT CUSHION ELEMENT
(1) From under the vehicle, remove the appropri-
ate seats four retaining nuts.
(2) From inside the vehicle, pull the seat up, off
the mounting studs and lay it back, up against one of
the rear seats.
(3) Locate the heated seat module, attached to the
bottom of the seat cushion pan. Remove the heated
seat module from the seat cushion pan. Do not dis-
connect the electrical connectors at this time.
(4) Locate the green 4-way electrical connector,
connected to the heated seat module. Disconnect the
green 4-way connector from the heated seat module.
(5) Check for continuity between the two outboard
circuit cavities of the wire harness connector (Pins
1&4). There should be continuity. If OK, refer to
Heated Seat Module Diagnosis and Testing in the
Electronic Control Modules section of the service
manual for complete system testing procedures. If
not OK, install a replacement heated seat cushion
element. Refer to the procedure in this section.
SEAT BACK ELEMENT
(1) From under the vehicle, remove the appropri-
ate seats four retaining nuts.
(2) From inside the vehicle, pull the seat up and
off the mounting studs and lay it back, up against
one of the rear seats.
(3) Locate the heated seat module, attached to the
bottom of the seat cushion pan. Remove the heated
seat module from the seat cushion pan. Do not dis-
connect the electrical connectors at this time.
(4) Locate the gray 2-way electrical connector, con-
nected to the heated seat module. Disconnect the
2-way connector from the heated seat module.
(5) Check for continuity between the two circuit
cavities of the 2-way wire harness connector. There
should be continuity. If OK, refer to Heated Seat
Module Diagnosis and Testing in the Electronic Con-
trol Modules section of the service manual for com-
plete system testing procedures. If not OK, install a
replacement heated seat back element. Refer to the
procedure in this section.
RSHEATED SEAT SYSTEM8G-11
DRIVER HEATED SEAT SWITCH (Continued)
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HORN SYSTEM TEST
CONDITION POSSIBLE CAUSE CORRECTION
HORN SOUNDS CONTINUOUSLY.
NOTE: IMMEDIATELY UNPLUG HORN
RELAY IN THE IPM.(1) FAULTY HORN RELAY. (1) REFER TO HORN RELAY TEST.
(2) HORN CONTROL
CIRCUIT TO RELAY
SHORTED TO GROUND.(2) CHECK TERMINAL 85 IN IPM
FOR CONTINUITY TO GROUND. IF
CONTINUITY TO GROUND
INDICATES:
(A) STEERING WHEEL HORN
SWITCH/LEAD SHORTED TO
GROUND.
(B) WIRING HARNESS SHORTED
TO GROUND. FIND THE SHORT
AND REPAIR AS NECESSARY.
(3) PINCHED HORN
SWITCH WIRE UNDER
DRIVER AIRBAG MODULE.(3) REPLACE DRIVER AIRBAG
MODULE TRIM COVER.
(4) FAULTY HORN SWITCH. (4) REPLACE DRIVER AIRBAG
MODULE TRIM COVER.
(5) FAULTY CLOCKSPRING. (5) REPLACE CLOCKSPRING.
(6) FAULTY FRONT
CONTROL MODULE.(6) REFER TO ELECTRONIC
CONTROL MODULES/FRONT
CONTROL MODULE.
HORN SOUND INTERMITTENTLY AS
THE STEERING WHEEL IS TURNED.(1) HORN RELAY
CONTROL CIRCUIT X3 IS
SHORTED TO GROUND
INSIDE STEERING
COLUMN OR WHEEL.(1) REMOVE DRIVER AIRBAG
MODULE AND/OR WHEEL. CHECK
FOR RUBBING OR LOOSE
WIRE/CONNECTOR, REPAIR AS
NECESSARY.
(2) PINCHED HORN
SWITCH WIRE UNDER
DRIVER AIRBAG MODULE.(2) REPLACE DRIVER AIRBAG
MODULE TRIM COVER.
(3) FAULTY HORN SWITCH. (3) REPLACE DRIVER AIRBAG
MODULE TRIM COVER.
(4) FAULTY CLOCKSPRING. (4) REPLACE CLOCKSPRING.
HORN DOES NOT SOUND (1) CHECK FUSE 8 IN
INTELLIGENT POWER
MODULE.(1) REPLACE FUSE IF BLOWN
REPAIR AS NECESSARY.
(2) NO VOLTAGE AT HORN
RELAY TERMINALS 30 &
86, AND FUSE IS OK.(2) NO VOLTAGE, REPAIR THE
CIRCUIT AS NECESSARY.
(3) OPEN CIRCUIT FROM
TERMINAL 85 OF THE
HORN RELAY TO HORN
SWITCH, X3 CIRCUIT.(3) REPAIR CIRCUIT AS
NECESSARY.
(4) FAULTY OR DAMAGED
HORN.(4) VOLTAGE AT HORN WHEN
HORN SWITCH IS PRESSED,
REPLACE HORN.
8H - 2 HORNRS
HORN SYSTEM (Continued)
ProCarManuals.com

CONDITION POSSIBLE CAUSE CORRECTION
(5) FAULTY HORN SWITCH. (5) REPLACE DRIVER AIRBAG
MODULE TRIM COVER.
(6) FAULTY CLOCKSPRING. (6) REPLACE CLOCKSPRING.
(7) FAULTY FRONT
CONTROL MODULE.(7) REFER TO ELECTRONIC
CONTROL MODULES/FRONT
CONTROL MODULE.
FUSE BLOWS WHEN HORN SOUNDS (1) SHORT CIRCUIT IN
HORN OR HORN WIRING.(1) REMOVE HORN RELAY, CHECK
FOR SHORTED HORN OR HORN
WIRING. DISCONNECT HORN WIRE
HARNESS TO ISOLATE SHORT
AND REPAIR AS NECESSARY.
(2) FAULTY CLOCKSPRING. (2) REPLACE CLOCKSPRING.
FUSE BLOWS WITHOUT BLOWING
HORN(1) SHORT CIRCUIT. (1) REMOVE RELAY, INSTALL NEW
FUSE, IF FUSE DOES NOT BLOW
REPLACE HORN RELAY. IF FUSE
BLOWS WITH RELAY REMOVED,
CHECK FOR SHORT TO GROUND
WITH OHMMETER ON CIRCUIT
BETWEEN TERMINALS 30 & 86
AND THE FUSE TERMINAL. REPAIR
AS NECESSARY.
(2) FAULTY CLOCKSPRING. (2) REPLACE CLOCKSPRING.
HORN
DIAGNOSIS AND TESTING - HORN
HORN
(1) Disconnect wire connector at horn.
(2) Using a voltmeter, connect one lead to ground
terminal and the other lead to the positive wire ter-
minal (Fig. 1).
(3) Depress the horn switch, battery voltage
should be present.
(4) If no voltage, refer toHORNS WILL NOT
SOUND. If voltage is OK, go to step Step 5.
(5) Using ohmmeter, test ground wire for continu-
ity to ground.
(6) If no ground repair as necessary.
(7) If wires test OK and horn does not sound,
replace horn.
HORNS SOUND CONTINUOUSLY
CAUTION: Continuous sounding of horns may
cause relay to fail.The horn switch (membrane) sometimes can be the
cause without the switch being depressed.
(1) Remove the horn relay from the intelligent
power module.
(2) Using a continuity tester, test continuity from
the X3 cavity of the horn relay to ground. 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.
(a) If continuity is detected, proceed to step Step
3.
(b) If NO continuity, replace the horn relay.
(3) Remove the airbag trim cover from the steering
wheel and disengage horn connector.
(4) Install horn relay into Integrated Power Mod-
ule (IPM).
(a) If horn does not sound, replace airbag trim
cover.
(b) If horn sounds, repair grounded X3 circuit
from IPM to clockspring in the steering column.
HORNS WILL NOT SOUND
Check horn fuse#8intheIPM. If fuse is blown,
check for a shorted switch in the airbag module. and
refer to FUSE BLOWN section. If fuse is OK, refer to
FUSE OK section.
RSHORN8H-3
HORN SYSTEM (Continued)
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from Fahrenheit to Celsius by selecting the desired
U.S./Metric option from the customer programmable
features. The displayed temperature is not an instant
reading of conditions, but an average temperature. It
may take the temperature display several minutes to
respond to a major temperature change, such as driv-
ing out of a heated garage into winter temperatures.
When the ignition switch is turned to the Off posi-
tion, the last displayed temperature reading stays in
the electronic control modules (CT, CMTC, EVIC)
memory. When the ignition switch is turned to the
On position again, the electronic module will display
the memory temperature for one minute; then update
the display to the current average temperature read-
ing within five minutes.
The temperature function is supported by an ambi-
ent temperature sensor. The sensor is mounted out-
side the passenger compartment near the front and
center of the vehicle, and is hard wired to the Front
Control Module (FCM). The FCM sends temperature
status messages to the module over the J1850 PCI
data bus circuit.
Following are general descriptions of the major
components used in the overhead console. Refer to
Wiring Diagrams for complete circuit schematics.
OPERATION
Refer to the vehicle Owner's Manual for specific
operation of each overhead console and its systems.
DIAGNOSIS AND TESTING - OVERHEAD
CONSOLE
If the problem with the overhead console is an
inaccurate or scrambled display, refer toSelf-Diag-
nostic Testbelow. If the problem with the overhead
console is incorrect Vacuum Fluorescent Display
(VFD) dimming levels, use a DRB IIItscan tool and
the proper Diagnostic Procedures manual to test for
the correct dimming message inputs being received
from the Body Control Module (BCM) or Front Con-
trol Module (FCM) over the J1850 Programmable
Communications Interface (PCI) data bus circuit. If
the problem is a no-display condition, use the follow-
ing procedures. For complete circuit diagrams, refer
toOverhead Consolein the Wiring Diagrams sec-
tion of the service manual.
(1) Check the fused B(+) fuse in the integrated
power module. 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
in the integrated power module. If OK, go to Step 3.
If not OK, repair the open fused B(+) circuit to the
fused B(+) fuse in the integrated power module as
required.(3) Check the fused ignition switch output (run/
start) fuse in the integrated power module. If OK, go
to Step 4. If not OK, repair the shorted circuit or
component as required and replace the faulty fuse.
(4) Turn the ignition switch to the On position.
Check for battery voltage at the fused ignition switch
output (run/start) fuse in the integrated power mod-
ule. If OK, go to Step 5. If not OK, repair the open
fused ignition switch output (run/start) circuit to the
ignition switch as required.
(5) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Remove the overhead console. Check for continuity
between the ground circuit cavity of the roof wire
harness connector for the electronics module and a
good ground. There should be continuity. If OK, go to
Step 6. If not OK, repair the open ground circuit to
ground as required.
(6) Connect the battery negative cable. Check for
battery voltage at the fused B(+) circuit cavity of the
roof wire harness connector for the electronics mod-
ule. If OK, go to Step 7. If not OK, repair the open
fused B(+) circuit to the fused B(+) fuse in the inte-
grated power module as required.
(7) Turn the ignition switch to the On position.
Check for battery voltage at the fused ignition switch
output (run/start) circuit cavity of the roof wire har-
ness connector for the electronics module. If OK,
refer toSelf-Diagnostic Testlater this group for
further diagnosis of the electronics module and the
J1850 PCI data bus circuit. If not OK, repair the
open fused ignition switch output (run/start) circuit
to the fuse in the integrated power module as
required.
SELF-DIAGNOSTIC TEST
A self-diagnostic test is used to determine that the
electronics module is operating properly, and that all
the J1850 PCI data bus messages are being received
for initial operation. Initiate the self-diagnostic test
as follows:
(1) With the ignition switch in the Off position, on
Electronic Vehicle Information Center (EVIC) and
Compass Mini-Trip Computer (CMTC) equipped vehi-
cles simultaneously depress and hold theSTEP and
the RESET buttons. On Compass Temperature
Module (CT) equipped vehicles depress theC/T and
the US/M push buttons.
(2) Turn the ignition switch to the On position.
(3) Following completion of these tests, the elec-
tronics module will display one of the following mes-
sages:
a.Pass Self Test (EVIC only), PASS (CT,
CMTC)- The electronics module is working properly.
b.Failed Self Test (EVIC only), FAIL (CT,
CMTC)- The electronics module has an internal fail-
8M - 2 MESSAGE SYSTEMSRS
OVERHEAD CONSOLE (Continued)
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ELECTRONIC VEHICLE INFO
CENTER
DESCRIPTION
The Electronic Vehicle Information Center (EVIC)
is a module located in the overhead console on some
models. The EVIC module features a large Vacuum
Fluorescent Display (VFD) screen for displaying
information, and back-lit push button switches
labeled C/T (compass/thermometer), RESET, STEP,
and MENU.
The EVIC module contains a central processing
unit and interfaces with other electronic modules in
the vehicle over the Programmable Communications
Interface (PCI) J1850 data bus circuit. The PCI data
bus circuit allows the sharing of sensor information.
This helps to reduce wire harness complexity, reduce
internal controller hardware, and reduce component
sensor current loads. At the same time, this system
provides increased reliability, enhanced diagnostics,
and allows the addition of many new feature capabil-
ities.
The EVIC ªMenuº push button provides the vehicle
operator with a user interface, which allows the
selection of several optional customer programmable
electronic features to suit individual preferences.
Refer toELECTRONIC VEHICLE INFORMA-
TION CENTER PROGRAMMINGin the Service
Procedures section of this group for more information
on the customer programmable feature options.
If the vehicle is equipped with the optional univer-
sal transmitter transceiver, the EVIC will also dis-
play messages and an icon indicating when the
universal transmitter transceiver is being trained,
which of the three transmitter buttons is transmit-
ting, and when the transceiver is cleared.
Data input for all EVIC functions, including VFD
dimming level, is received through the J1850 PCI
data bus circuit. The EVIC module uses its internal
programming and all of its data inputs to calculate
and display the requested data. If the data displayed
is incorrect, perform the self-diagnostic tests as
described in this group. If these tests prove inconclu-
sive, the use of a DRBIIItscan tool and the proper
Diagnostic Procedures manual are recommended for
further testing of the EVIC module and the J1850
PCI data bus circuit.
The EVIC module cannot be repaired, and is avail-
able for service only as a unit. This unit includes the
plastic module and display lens. If any of these com-
ponents is faulty or damaged, the complete EVIC
module must be replaced.
OPERATION
The EVIC has access to both non-switched and
ignition switched sources of battery current so that
some of its features remain operational at any time,
while others may only operate with the ignition
switch in the On position. When the ignition switch
is turned to the On position, the EVIC module VFD
will return to the last function being displayed before
the ignition was turned to the Off position.
The compass/thermometer display is the normal
EVIC display. With the ignition switch in the On
position, momentarily depressing and releasing the
C/T (compass/thermometer) push button switch will
cause the EVIC to return to the compass/thermome-
ter/trip computer display mode from any other mode.
While in the compass/thermometer/trip computer dis-
play mode, momentarily depressing and releasing the
Step push button will step through the available trip
computer display options.
The EVIC trip computer features several functions
that can be reset. The functions that can be reset
are: average fuel economy, trip odometer and elapsed
time. With the ignition switch in the On position and
with one of the functions of the trip computer that
can be reset currently displayed, depressing the
Reset push button twice within three seconds will
perform a global reset, and all of the trip computer
information that can be reset will be reset to zero.
With the ignition switch in the On position and the
function that is to be reset currently displayed,
momentarily depressing and releasing the Reset
push button once will perform a local reset, and only
the value of the displayed function will be reset to
zero. A global or local reset will only occur if the
function currently displayed is a function that can be
reset. The distance to service function can also be
reset using the local reset method, but it will reset
back to the Service Interval distance that is set in
the EVIC programmable features mode. Refer to
ELECTRONIC VEHICLE INFORMATION CEN-
TER PROGRAMMINGin the Service Procedures
section of this group for more information on setting
the Service Interval.
For more information on the features, control func-
tions and setting procedures for the EVIC module,
see the owner's manual in the vehicle glove box.
DIAGNOSIS AND TESTING - ELECTRONIC
VEHICLE INFORMATION CENTER
Electronic Vehicle Information Center (EVIC) data
is obtained from the Body Control Module (BCM) on
the J1850 Data Bus circuit. The EVIC will display
dashes (- -) for any of the screens it did not receive
the bus messages. The label corresponding to the
missing information will be lit. If no EVIC data is
displayed, check the J1850 Data Bus circuit commu-
8M - 6 MESSAGE SYSTEMSRS
ProCarManuals.com

NOTE: IF A NEW EVIC MODULE HAS BEEN
INSTALLED, THE COMPASS WILL HAVE TO BE
CALIBRATED AND THE VARIANCE SET. REFER TO
COMPASS VARIATION ADJUSTMENT AND COM-
PASS CALIBRATION IN THE SERVICE PROCE-
DURES SECTION OF THIS GROUP FOR THE
PROCEDURES.
COMPASS/MINI-TRIP
COMPUTER
DESCRIPTION
The Compass Mini-Trip Computer (CMTC) and
Compass Temperature (CT) computer are modules
located in the overhead console. Vehicles are
equipped with either the CMTC or the CT computers
not both. The CMTC is different in the fact that it is
equipped with the mini-trip feature. The CMTC, CT
consists of a electronic control module with a vacuum
fluorescent display (VFD) and function switches. The
CMTC, CT consists of a electronic module that dis-
plays compass, trip computer (CMTC only), and tem-
perature features. Actuating the STEP push button
(CMTC only) will cause the CMTC to change mode of
operation when ignition is ON. Actuating the STEP
push button (CMTC only) will cause the CMTC to
change mode of operation when ignition is ON.
Example:
²Average miles per gallon (ECO)
²Distance to empty (DTE)
²Instant miles per gallon (ECO)
²Trip odometer (ODO)
²Elapsed time (ET)
²Off
Actuating the C/T push button will cause the
CMTC, CT to change to Compass/Temperature dis-
play.
OPERATION
The Compass Mini-Trip Computer (CMTC), Com-
pass Temperature (CT) module in the overhead con-
sole has buttons used to select various functions. The
CMTC, CT selector buttons will not operate until the
ignition is in the RUN position.
When the ignition switch is first turned to the
RUN position the CMTC, CT display;
²Blanks momentarily
²All segments of the VFD will light for one sec-
ond
²Blanks momentarily
²Returns to the last mode setting selected before
the ignition was last switched OFF.
DIAGNOSIS AND TESTING - COMPASS
MINI-TRIP COMPUTER
Compass Mini-Trip Computer (CMTC) and Com-
pass Temperature (CT) data is obtained from the
Body Control Module (BCM) on the J1850 Data Bus
circuit. The CMTC and CT will display dashes (- -)
for any of the screens it did not receive the bus mes-
sages. The label corresponding to the missing infor-
mation will be lit. If no compass mini-trip computer
data is displayed, check the J1850 Data Bus circuit
communications and the BCM. If the brightness level
is improper check the J1850 Data Bus circuit.
The DRB IIItis recommended for checking the
J1850 Data Bus circuit and the BCM. Perform the
CMTC, CT self diagnosis before replacing the CMTC
or CT module.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove overhead console. Refer to Overhead
Console Removal and Installation in this section(Re-
fer to 8 - ELECTRICAL/OVERHEAD CONSOLE -
REMOVAL).
(3) Remove the screws holding Compass Mini-Trip
Computer module in the overhead console.
(4) Remove CMTC module from console assembly.
INSTALLATION
(1) Position the compass mini-trip computer mod-
ule in the overhead console.
(2) Install the ten screws holding the compass
mini-trip computer module in the overhead console.
(3) Install the overhead console. Refer to Overhead
Console Removal and Installation in this section.
(4) Connect the battery negative cable.
NOTE: If a new module has been installed, the com-
pass will have to be calibrated and the variance set.
Refer to Compass Variation Adjustment and Com-
pass Calibration in the Service Procedures section
of this group for the procedures.
UNIVERSAL TRANSMITTER
DESCRIPTION
On some RS models a Universal Transmitter trans-
ceiver is standard factory-installed equipment. The
universal transmitter transceiver is integral to the
Electronic Vehicle Information Center (EVIC) and the
Compass Mini-Trip Computer (CMTC), which is
located in the overhead console. The only visible com-
ponent of the universal transmitter are the three
transmitter push buttons centered between the mod-
RSMESSAGE SYSTEMS8M-9
ELECTRONIC VEHICLE INFO CENTER (Continued)
ProCarManuals.com

ules push buttons located just rearward of the dis-
play screen in the overhead console. The three
universal transmitter push buttons are identified
with one, two or three light indicators so that they be
easily identified by sight or by feel.
Each of the three universal transmitter push but-
tons controls an independent radio transmitter chan-
nel. Each of these three channels can be trained to
transmit a different radio frequency signal for the
remote operation of garage door openers, motorized
gate openers, home or office lighting, security sys-
tems or just about any other device that can be
equipped with a radio receiver in the 286 to 399
MegaHertz (MHz) frequency range for remote opera-
tion. The universal transmitter is capable of operat-
ing systems using either rolling code or non-rolling
code technology.
The electronics module displays messages and a
small house-shaped icon with one, two or three dots
corresponding to the three transmitter buttons to
indicate the status of the universal transmitter. The
EVIC messages are:
²Cleared Channels- Indicates that all of the
transmitter codes stored in the universal transmitter
have been successfully cleared.
²Training- Indicates that the universal trans-
mitter is in its transmitter learning mode.
²Trained- Indicates that the universal transmit-
ter has successfully acquired a new transmitter code.
²Transmit- Indicates that a trained universal
transmitter button has been depressed and that the
universal transmitter is transmitting.
The universal transmitter cannot be repaired, and
is available for service only as a unit with the EVIC
or CMTC modules. If any of these components is
faulty or damaged, the complete EVIC or CMTC
module must be replaced.
OPERATION
The universal transmitter operates on a non-
switched source of battery current so the unit will
remain functional, regardless of the ignition switch
position. For more information on the features, pro-
gramming procedures and operation of the universal
transmitter, see the owner's manual in the vehicle
glove box.
DIAGNOSIS AND TESTING - UNIVERSAL
TRANSMITTER
If the universal transmitter is inoperative, but the
Electronic Vehicle Information Center (EVIC) or
Compass Mini-Trip Computer is operating normally,
see the owner's manual in the vehicle glove box for
instructions on training the universal transmitter.
Retrain the universal transmitter with a known good
transmitter as instructed in the owner's manual andtest the universal transmitter operation again. If the
unit is still inoperative, replace the faulty universal
transmitter and EVIC/CMTC module as a unit. If
both the universal transmitter and the EVIC/CMTC
module are inoperative, refer toOverhead Console
Diagnosis and Testingearlier in this group for fur-
ther diagnosis. For complete circuit diagrams, refer
toOverhead Consolein Wiring Diagrams.
AMBIENT TEMP SENSOR
DESCRIPTION
Ambient air temperature is monitored by the over-
head console through ambient temperature messages
received from the Front Control Module (FCM) over
the Programmable Communications Interface (PCI)
J1850 data bus circuit. The FCM receives a hard
wired input from the ambient temperature sensor.
The ambient temperature sensor is a variable resis-
tor mounted to a bracket that is secured with a screw
to the right side of the headlamp mounting module
grille opening, behind the radiator grille and in front
of the engine compartment.
Refer toFront Control Modulein Electronic
Control 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 Front Control Module. The resis-
tance in the sensor changes as temperature changes,
changing the temperature sensor signal circuit volt-
age to the Front Control Module. Based upon the
resistance in the sensor, the Front Control Module
senses a specific voltage on the temperature sensor
signal circuit, which it is programmed to correspond
to a specific temperature. The Front Control Module
then sends the proper ambient temperature mes-
sages to the EVIC, CMTC over the PCI J1850 data
bus.
The thermometer function is supported by the
ambient temperature sensor, a wiring circuit, the
Front Control Module, the Programmable Communi-
cations Interface (PCI) data bus, and a portion of the
Electronics module. If any portion of the ambient
temperature sensor circuit fails, the Front Control
Module will self-diagnose the circuit.
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-
8M - 10 MESSAGE SYSTEMSRS
UNIVERSAL TRANSMITTER (Continued)
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POWER LIFTGATE SYSTEM
DESCRIPTION
Some vehicles are equipped with an automatic
opening and closing power liftgate system (Fig. 1).
This power liftgate system is a complex system con-
sisting of many components. Some of these compo-
nents are the liftgate gear motor assembly, latch
assembly, lift gear and rod, liftgate control module,
chime/thermistor, full open switch, engage actuator,
pinch sensor, liftgate handle switch, overhead console
switch, key fob switches (Fig. 2), pawl switch and
ratchet switch.
The power liftgate system has its own door control
module, located on the vehicles left body D-pillar
behind the trim panel. (Refer to 8 - ELECTRICAL/
ELECTRONIC CONTROL MODULES/DOOR CON-
TROL MODULE - DESCRIPTION) The power
liftgate gear motor assembly is located just above the
control module. The latch assembly is located in the
bottom center of the power liftgate, below the exte-
rior liftgate handle switch. The power liftgate full
open switch, engage actuator, lift gear and rod are
part of the liftgate gear motor assembly. The pawl
and ratchet switches are part of the latch assembly.The pinch sensor or sensors are located along the
right and left sides of the power liftgate, just above
the body line. The liftgate handle switch is an power
release switch and is located in the rear light bar
assembly, just above the license plate. The overhead
console switch is an power open and close command
switch located in the vehicles overhead console.
Safety is of the utmost concern with the power lift-
gate system. Software technology has enabled the
power liftgate control module to detect resistance to
liftgate travel, which allows the power liftgate to stop
and reverse direction anytime an obstruction is felt
or any of the command switches are operated (only in
closing direction). Battery voltage is supplied to the
power liftgate system through a 40 amp fuse, located
in the Intelligent Power Module (IPM) assembly (Fig.
3). In the unlikely event that the power liftgate sys-
tem develops a fault the power liftgate can still be
operated manually with a key, just like a standard
manual liftgate.
Fig. 1 POWER LIFTGATE INTRODUCTION
8N - 2 POWER LIFTGATE SYSTEMRS
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