Console: Testing and Inspection

If the problem with the overhead console is an inaccurate or scrambled display, refer to Self-Diagnostic 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 Control Module (FCM) over the J1850 Programmable Communications Interface (PCI) data bus circuit. If the problem is a no-display condition, use the following procedures. For complete circuit diagrams, refer to Overhead Console in the Wiring Diagrams section 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 module. 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 module. If OK, go to Step 7. If not OK, repair the open fused B(+) circuit to the fused B(+) fuse in the integrated 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 harness 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 vehicles 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 electronics module will display one of the following messages:
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 failure. The electronics module is faulty and must be replaced.
c. Failed J1850 Communication (EVIC only), BUS (CT, CMTC) - The electronics module is not receiving proper message input through the J1850 PCI data bus circuit. This can result from one or more faulty electronic modules in the vehicle, or from a faulty PCI data bus. The use of a DRB III scan tool and the proper Diagnostic Procedures manual are required for further diagnosis.

NOTE:
- If the compass functions, but accuracy is suspect, it may be necessary to perform a variation adjustment. This procedure allows the compass unit to accommodate variations in the earth's magnetic field strength, based on geographic location. Refer to Compass Variation Adjustment in the Service Procedures section of this group.
- If the compass reading displays dashes, and only "CAL" appears in the display, demagnetizing may be necessary to remove excessive residual magnetic fields from the vehicle. Refer to Compass Demagnetizing in the Service Procedures section of this group.