Chart 2 PCM Power and Ground Check

Circuit Description

The PCM is fed battery voltage at all times at pins '2C4' and '2D4' through CKT 480 from the engine compartment fuse block, fuse 'B13'. The PCM is also fed IGN 1 (HOT IN RUN, BULB TEST and START) at pin '2D5' through CKT 1276 from the engine fuse block fuse 'A9'. 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 G102.

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 C101 pin 'A2'. If voltage is not measured at either pin, check fuse 'B13' and CKT 480 to C101 pin 'A2' for an open.
3. Checking CKT 1276 and fuse 'A9' 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 S234. If voltage measures above 0.1 volt on all four wires, repair the open from S234 to G102.
5. Checking for an open in CKT 450 or inside the PCM.
6. Checking if the Data line is open shorted to ground or voltage causing a PCM problem.