PCM Learning Ability

The Powertrain Control Module (PCM) has a learning ability that allows it to make corrections for minor variations in the fuel system to improve driveability and engine idle. If the battery is disconnected, or the PCM is replaced, the PCM must go through a learning process. Until the PCM has gone through this learning process, a change may be noted in the driveability, or idle of the vehicle. To allow the PCM to relearn, the following steps must be performed:
- Start the vehicle and run the engine until normal operating temperature is obtained.
- Drive the vehicle at part throttle, with moderate acceleration and idle conditions until normal performance returns.
- Park the vehicle and engage the parking brake with engine running.
- Place the transaxle in Drive.
- Allow the vehicle to idle for about two minutes, until engine idle stabilizes. Make sure engine is at operating temperature.

The Transaxle Controller Module (TCM) portion of the PCM also has a learning ability to achieve smooth shifts. If the battery is disconnected, the TCM will lose the fine tuning of shift points, which have been learned while driving the vehicle. Connecting the battery will not reset the TCM adaptive parameter. The adaptives can only be reset using the Service Stall System (SSS), or using a Scan tool. To relearn the shifts, the vehicle should be driven. (Refer to the "Learn-in Procedure") Learn-In Procedure