Failure Code Determination

During any diagnostic procedure, "hard failure" codes MUST be distinguished from "intermittent failure" codes. Diagnostic charts CANNOT be used to analyze "intermittent failure" codes, except as noted under Diagnostic Procedure. To determine "hard failure" codes, proceed as follows:

1. Turn ignition on. Enter diagnostics. Read and record all stored trouble codes. Exit diagnostics and clear memory. Reconnect negative battery cable.
2. Apply parking brake and place transmission in neutral (manual) or park (automatic). Block drive wheels. Start engine. Enter diagnostic mode. Operate engine below 800 RPM for 5 minutes.
3. If test lamp flashes trouble codes (except "13", "44" and "45"), note and record trouble codes. This will reveal "hard failures". Codes "13", "44" and "45" require engine operation at partial throttle with an engine load (road test) for an extended period of time before fault is detected.
   NOTE: Trouble code "15" fault will only display after 5 minutes of engine operation. Trouble code "12" will display only during time of no reference pulses received by ECM; it will never be stored as a malfunction.
4. If test lamp does not flash trouble codes (except "13", "44" and "45"), all trouble codes stored in memory were "intermittent failures", except as noted under Diagnostic Procedure.
   NOTE: Grounding test terminal with engine running will force engine to operate in closed loop mode if engine is warm and oxygen sensor is hot. If test lamp does not glow while in closed loop, C-4 system is operating properly.