Checking Powertrain Control Module Power & Ground Circuits (4.7L)

Possible Causes

PCM Fused B+ Circuit
PCM Fused Ignition Switch Output Circuit
PCM Ground Circuits

CAUTION: DO NOT probe the Powertrain Control Module (PCM) harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal-to-pin connection. Install Miller Special Tool (8815) to perform diagnosis.

Test Procedure

Turn the ignition off. Disconnect the PCM harness connectors. See Figure . Using a 12-volt test light connected to ground, probe the PCM C1 fused B+ circuit in the appropriate terminal of the Miller Special Tool (8815). See Figure . Does the test light illuminate brightly? If yes, go to next step. If no, repair the PCM C1 fused B+ circuit for an open. Check related fuses and repair as necessary.
Turn the ignition on, with the engine off. Using 12-volt test light connected to ground, probe the fused ignition switch output circuits in the appropriate terminals of the Miller Special Tool (8815). See Figure . Does the test light illuminate brightly? If yes, go to next step. If no, repair the fused ignition switch output circuit(s) for an open. Check related fuses and repair as necessary.
Turn the ignition off. Using 12-volt test light connected to battery voltage, probe the PCM (C1 and C4) ground circuits in the appropriate terminals of the Miller Special Tool (8815). See Figure and Figure . Does the test light illuminate brightly? If yes, the test is complete. If no, repair the PCM ground circuit(s) for an open.