Circuit Description
WARNING: This page is about a different car, the 2006 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.
The body control module (BCM) monitors the brake pedal position sensor. When the brake pedal is applied, the BCM detects a predetermined voltage signal. The BCM sends a GMLAN serial data message to the transmission control module (TCM) and to the engine control module (ECM) indicating the status of the stop lamps.