Hard Or Intermittent Trouble Code Determination

During any diagnostic procedure, it must be determined if codes are hard failure codes or intermittent failure codes. A hard failure indicates that a problem is currently present. Diagnostic charts do not usually provide intermittent code diagnosis. To determine hard codes and intermittent codes, proceed as follows:

1. Manually enter diagnostic mode. Record all stored trouble codes. Exit diagnostic mode, and clear trouble codes. See CLEARING TROUBLE CODES .
2. Apply parking brake, and place transmission in Neutral or Park. Block drive wheels, and start engine. TRANS or SERVICE ENGINE SOON light should go out. Operate warm engine at specified curb idle for 2 minutes, and note TRANS or SERVICE ENGINE SOON light.
3. If TRANS or SERVICE ENGINE SOON light does not come on, codes are intermittent failures. If TRANS or SERVICE ENGINE SOON light comes on, manually enter diagnostic mode. Record trouble codes. If same codes reappear, they are hard failure codes. It may be necessary to road test vehicle in order to reset hard failure codes.