Chart 2 PCM Power and Ground Check

Chart 2:

PCM Power And Ground Circuit:

CIRCUIT DESCRIPTION:
The PCM is fed battery voltage at all times at pins "2C4" and "2D4" through CKT 480 from the trunk compartment fuse block, fuse "B7." The PCM is also fed IGN 1 (HOT IN RUN, BULB TEST and START) at pin "2D5" through CKT 1039 from the console fuse block fuse A7. The PCM needs both battery and IGN 1 voltages to operate.

The PCM also has four grounding points at pins "2C2," "2C3," "2D2," and "2D3" through CKT 450 to G104.

NOTES ON FAULT TREE:
1. Checking for data line codes that would indicate that the entire data line is down.

2. Checking for battery voltage on CKT 480. If voltage is measured at one pin and not the other, check CKT 480 for an open to S232. If voltage is not measured at either pin, check fuse "B7" and CKT 480 to S232 for an open.

3. Checking CKT 1039 and fuse "A7" for an open.

4. Checking CKT 450 for an open. If voltage measures above 0.1 volt on 1 to 3 wires, repair open to S229. If voltage measures above 0.1 volt on all four wires, repair the open from S229 to G104.

5. Checking for an open in CKT 450 or inside the PCM.

6. Checking if an open short to ground or voltage on the Data Link is causing a PCM problem.