Powertrain Control Module (PCM)
WARNING: This page is about a different car, the 2006 Lincoln Navigator and 2006 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.
The PCM communicates on the high speed CAN. The PCM controls the engine for better fuel economy, emissions control, failure mode detection and storage. The PCM also controls 4x4 functionality. For additional information, refer to INTRODUCTION - GASOLINE article .