Engine Controls
Vehicles equipped with engine/powertrain control modules may require a computer relearn procedure after the ECM/PCM is reset or vehicle battery is disconnected. Vehicle computers memorize and store vehicle operation patterns for optimum driveability and performance. When this memory is lost, it may result in a driveability problem. Depending on the vehicle and how it is equipped, the following driveability problems may exist:
- Rough or unstable idle.
- Hesitation or stumble.
- Rich or lean running.
- Poor fuel mileage.
- Harsh or poor transmission/transaxle shift quality.
Driveability problems may occur during the computer relearn stage. To accelerate computer relearn process after ECM/PCM reset or battery removal and installation, specified computer relearn procedures should be performed. See appropriate procedures for specified manufacturer.