Chrysler Town, Dodge Caravan. Manual - part 114

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 III

t is 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 8 - ELEC-

TRICAL/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 8 -

ELECTRICAL/OVERHEAD CONSOLE - INSTALLA-
TION).

(4) Connect the battery negative cable.

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
compass calibration in standard 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)

modules,

which is located in the overhead console. The only
visible component of the universal transmitter are
the three transmitter push buttons centered between
the modules push buttons located just rearward of
the display 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:

• Cleared Channels - Indicates that all of the

transmitter codes stored in the universal transmitter
have been successfully cleared.

• Training - Indicates that the universal trans-

mitter is in its transmitter learning mode.

• Trained - Indicates that the universal transmit-

ter has successfully acquired a new transmitter code.

• Transmit - 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) is oper-
ating normally, see the owner’s manual in the vehicle
glove box for instructions on training the Transmit-
ter. Retrain the Transmitter with a known good
transmitter as instructed in the owner’s manual and
test the Transmitter operation again. If the unit is
still inoperative, test the universal transmitter with
Radio Frequency Detector special tool. If both the

8M - 10

MESSAGE SYSTEMS

COMPASS/MINI-TRIP COMPUTER (Continued)

Transmitter and the EVIC module are inoperative,
refer to Electronic Vehicle Information Center
Diagnosis and Testing in this group for further
diagnosis. For complete circuit diagrams, refer to
Wiring Diagrams. (Fig. 5) as described below:

(1) Turn the Radio Frequency (RF) Detector ON. A

“chirp” will sound and the green power LED will
light. If the green LED does not light, replace the
battery.

(2) Hold the RF detector within one inch of the

TRAINED universal transmitter and press any of the
transmitters buttons.

(3) The red signal detection LEDs will light and

the tool will beep if a radio signal is detected. Repeat
this test three times.

STANDARD PROCEDURE

STANDARD PROCEDURE - SETTING
TRANSMITTER CODES

(1) Turn off the engine.
(2) Erase the codes by pressing the two outside

buttons. Release the buttons when the display con-
firms the operation (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.

(4) Release both buttons. Your universal transmit-

ter is now “trained”. To train the other buttons,
repeat Step 3 and Step 4. Be sure to keep your hand-
held transmitter in case you need to retrain the uni-
versal transmitter.

STANDARD PROCEDURE - ERASING
TRANSMITTER CODES

To erase the universal transmitter codes, simply

hold down the two outside buttons until the display
confirms the operation.

NOTE: Individual channels cannot be erased. Eras-
ing the transmitter codes will erase ALL pro-
grammed codes.

REMOVAL

(1) For universal transmitter removal and installa-

tion procedure, (Refer to 8 - ELECTRICAL/OVER-
HEAD

CONSOLE/COMPASS/MINI-TRIP

COMPUTER - REMOVAL and INSTALLATION).

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.

For more information on the Front Control Module

refer to the Electronic Control Modules section of this
manual. For complete circuit diagrams, refer to the
appropriate wiring information. The ambient temper-
ature 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

Fig. 5 RADIO FREQUENCY DETECTOR

1 - SIGNAL DETECTION LED’S
2 - POWER LED
3 - ON/OFF SWITCH
4 - 9V BATTERY

MESSAGE SYSTEMS

8M - 11

UNIVERSAL TRANSMITTER (Continued)

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 to Diagnosis 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 to Diagnosis and
Testing - Overhead Console in this group. 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 –40° C (–40° F), the sensor resis-
tance is 336.6 kilohms. At 60° C (140° F), the sensor
resistance is 2.49 kilohms. The sensor resistance
should read between these two values. If OK, refer to
Diagnosis and Testing - Ambient Temperature
Sensor Circuit in 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 Front 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.

(3) Check for continuity between the sensor return

circuit and the ambient temperature sensor signal
circuit cavities of the Front Control Module wire har-
ness 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 temperature 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 Front Control Module
wire harness connector and a good ground. There
should be no continuity. 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 Front
Control Module wire harness connector and a good
ground. There should be no continuity. If OK, refer to
Diagnosis and Testing - Overhead Console in
this group. If not OK, repair the shorted ambient
temperature sensor signal circuit as required.

REMOVAL

(1) Disconnect and isolate the battery negative

cable.

(2) From behind front bumper fascia, remove

screw holding sensor to radiator closure panel.

(3) Disconnect

the

sensor

electrical

connector.

Depress the connector retaining tab and pull the con-
nector straight off the ambient temperature sensor.

(4) Remove sensor from vehicle.