Overhead Console; Operation; Diagnosis And Testing - Overhead; Console - Chrysler Dodge Caravan 2002 Manual

8M - 2 MESSAGE SYSTEMS
OVERHEAD CONSOLE (Continued)
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 to Self-Diag-
nostic Test below. If the problem with the overhead
console is incorrect Vacuum Fluorescent Display
(VFD) dimming levels, use a DRB III scan 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
to Overhead Console in 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 to Self-Diagnostic Test later 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 the STEP and
the RESET buttons. On Compass Temperature
Module (CT) equipped vehicles depress the C/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-
RS