Principles of Operation: Pcm
WARNING: This page is about a different car, the 2005 Lincoln Navigator and 2005 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.
The PCM uses 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, See INTRODUCTION - GASOLINE article .