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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 2240 from the Engine Compartment Fuse/Relay Center, fuse D7. IGN 1 voltage (Hot in Run, Bulb Test or Start) is fed through CKT 639 and the Engine Compartment Fuse/Relay Center, fuse C7 to PCM connector C1 terminal 19 and C2 terminal 37. IGN 0 voltage (Hot in all positions except LOCK) is fed through the Engine Compartment Fuse Block fuse A1 and CKT 147 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 451 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.