Computers and Control Systems: Service Precautions

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

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

2. Follow diagnostic procedures as outlined in Computers and Control Systems / System Diagnosis.
3. Disconnect electronic engine controls from wire harness before measuring for continuity, resistance or energizing by using a 12-volt source.
4. Never measure voltage or resistance directly at the PCM.