Powertrain Control Module (PCM)
WARNING: This page is about a different car, the 2005 Ford Mustang. However, it is still accessible from the selected car via links, so may be relevant.
The PCM uses the high speed CAN for communication with the diagnostic tool and all the modules on the high speed CAN. The PCM controls the engine for better fuel economy, emissions control, failure mode detection and data storage. Refer to the INTRODUCTION - GASOLINE article for diagnosis and testing of the PCM.