Chart B-2 Loss of BCM Data to IPC

Chart B-2:

Display Circuit:

DESCRIPTION:

This chart is used because the odometer, at key on, read all zeroes and the courtesy lamps turned on when the switch was actuated. These symptoms indicate a loss of BCM data communication to the IPC, which is the result of one of several different possible problems.

NOTES ON FAULT TREE:

1. If the ALDL connector cover is off or loose, this could cause a break in the data circuit cutting off BCM communication to the IPC under certain electrical conditions. Should this be the case, securely connect the ALDL cover and return to the beginning of the SELF-DIAGNOSTIC CIRCUIT CHECK.

2. This step isolates the ALDL connector, the PCM/ECM and the programmer from the data circuit in order to determine the location of the fault. If the odometer reads actual accumulated miles, then the fault lies within the network between the ALDL connector, the PCM/ECM and the programmer.

3. If the CCP portion of the CCDIC has displays, the data line between the BCM and CCDIC has been verified good. A blank CCP indicates a problem in this segment of the circuit.

4. This step will determine if the condition is caused by the DERM, by isolating it from the circuit.

5. From the preceding steps, the problem must exist between the DERM pin A8 and the ALDL pin L. Removing the IPC and reconnecting the ALDL cover will add only the data line circuit from IPC RB10 to ALDL pin L, the known good circuit. If the CCP blanks when this is done, this circuit is the source of the fault.

6. This determines whether the fault is in the last portion of the 800 CKT or the IPC. By jumpering around the IPC, it is eliminated from the circuit, adding only the final portion of the 800 CKT to the known good circuit.