Body Control System Description and Operation: Gateway
WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The body control module (BCM) communicates functionally on both class 2 and controller area network (CAN) serial data buses. The BCM is the gateway between the buses and transfers serial data messages from one subnet to another. Diagnostic communication of the BCM with the scan tool is through class 2 serial data circuit.