Chart 2 PCM Power and Ground Check

Chart Number 2:

Service Engine Soon Light Circuit:

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) is fed battery voltage at all times at pins "2C4" and "2D4" through CKT 840 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 539 from the engine compartment 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 451 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 840. If voltage is measured at one pin and not the other, check CKT 840 for an open to C205 pin "X." If voltage is not measured at either pin, check fuse "B13" and CKT 840 to C205 pin "X" for an open.

3. Checking CKT 539 and fuse "A9" for an open.

4. Checking CKT 451 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 451 or inside the PCM.

6. Checking if the data line is open, shorted to ground, or voltage causing a PCM problem.