The engine computer or PCM/ECM manages the performance of the engine, the emissions system, and in some cases, controls the transmission and ABS systems. When replacing the PCM, first make sure there is no evidence of water getting into the area where the PCM is located or the new PCM could be ruined.
How to Replace the Engine Computer
Note: This is a general summary.
1. Disconnect both battery terminals and wait at least five minutes
2. Remove any shroud or cover on the PCM, as well as any fasteners that secure it
3. Connect a ground strap to your wrist and a suitable ground
4. Disconnect and remove the old PCM
5. Install the new PCM
6. Clean the PCM electrical connectors and then connect them to the new PCM
7. Install any covers that were removed
8. Reconnect both battery terminals and connect a suitable battery charger
9. With the key in the "ON" position, download any needed software into the new PCM
10. Clear any and all system codes and perform a Drive Cycle Test Drive to verify the repair