Diagnostic Procedure

If engine electrical diagnostic system check was performed, go to next step. If engine electrical diagnostic system check was not performed, go to ENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECK under ON-VEHICLE TESTING.
Connect scan tool to Data Link Connector (DLC). Turn ignition switch to RUN position. Using scan tool, observe specific DTC information for DTC P0620 from engine controls. If scan tool indicates DTC P0620 failed this ignition, go to next step. If scan tool indicates DTC P0620 passed this ignition, problem may be intermittent. Check wiring and connections, and see PRELIMINARY INSPECTION under TROUBLE SHOOTING.
Test generator turn-on signal circuit for a short to ground. See WIRING DIAGRAMS . If no problem exists, go to next step. If problem exists, repair circuit as necessary and then go to step 6 .
Inspect PCM harness connector for poor connections. If no problem exists, go to next step. If problem exists, repair as necessary and then go to step 6 .
Replace PCM. After replacement, reprogram PCM. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. After repairs are made, go to next step.
Review and record scan tool fail records data. Using scan tool, clear DTCs. Start engine. Using scan tool, observe specific DTC information for DTC P0620 until test runs. If scan tool indicates DTC P0620 passed this ignition, system is okay. If scan tool indicates DTC P0620 failed this ignition, go to step 2 .