Computers and Control Systems: Service Precautions

1. Always disconnect battery ground cable before servicing or replacing electronic engine controls.

NOTE: When the battery has been disconnected and reconnected, some abnormal drive symptoms may occur while the Powertrain Control Module (PCM) relearns its fuel trim. The vehicle may need to be driven 16 km (10 miles) or more to relearn the fuel trim.

2. Follow diagnostic procedures.
3. Disconnect electronic engine controls from wire harness before measuring for continuity, resistance.
4. Never measure voltage or resistance directly at the powertrain control module.