Body Control System Description and Operation: Gateway
WARNING: This page is about a different car, the 2006 Pontiac Torrent and 2006 Chevrolet Equinox. 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 high speed GMLAN serial data buses. The BCM is the gateway between the buses and transfers serial data messages from one subnet to another. Physical communication of the BCM with the scan tool is through class 2 serial data circuit.