To clear the codes from the memory of the PCM, either to determine if the malfunction will occur again or because the repair has been completed, the PCM power feed must be disconnected for at least 30 seconds. Depending on how the vehicle is equipped, the PCM power feed can be disconnected at the positive battery terminal "pigtail," the inline fuseholder that originates at the positive connection at the battery, or the PCM fuse in the fuse block. (The negative battery terminal may be disconnected, but other on-board memory data, such as preset radio tuning, will also be lost.)
Stored fault codes may be erased from memory at any time by using a suitable scan tool, or by removing power from the PCM for at least 30 seconds. It may be necessary to clear stored codes during diagnosis to check for any recurrence during a test drive, but the stored codes should be written down when retrieved. The codes may still be required for subsequent troubleshooting. Whenever a repair is complete, the stored codes should be erased and the vehicle test-driven to confirm the repair.