Circuit/System Description

The stop lamp switch signal circuit is a direct hardwire input from the engine control module (ECM) to the body control module (BCM) and transmission control module (TCM). The ECM monitors the stop lamp switch circuit to detect when the brake pedal has been applied. The BCM monitors the brake pedal position (BPP) sensor to determine when the brake pedal is applied. When the brake pedal is applied, the BCM sends a GMLAN serial data message to the ECM indicating that the brake pedal has been applied. The ECM sends a voltage signal on the stop lamp switch circuit to the BCM and TCM.