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Circuit Description
The PCM is fed battery voltage at all times at PCM connector C1 terminals 20 and 61 through CKT 240 from the Underhood Junction Block, fuse A1. IGN 1 voltage (Hot in Run, Bulb Test or Start) is fed through CKT 39 and the Underhood Junction Block, fuse C7 to PCM connector C1 terminal 19 and C2 terminal 37. IGN 0 voltage (Hot in all positions except LOCK) is fed from the ignition switch. Refer to Power and Ground Distribution, CKT 1390 to PCM connector C1 terminal 18. The PCM needs all of these inputs to function properly.

The PCM also has four grounding points: at terminals 21 and 60 of both PCM connectors C1 and C2. These terminals are grounded through CKT 1551 to ground G102.

Diagnostic Aids
Ensure that the battery is fully charged and tested before performing this check.

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
2. Checking battery power supply to the PCM.
5. Checking Ignition 0 voltage to the PCM.
7. Checking Ignition 1 and Ignition Supplement voltage to the PCM.
9. Checking ground supply to the PCM. If PCM grounds are good, perform the Powertrain Ground Check to diagnose other vehicle grounds that may cause driveability complaints.