Circuit/System Description

The stop lamp switch signal circuit is a direct hardwire input to the engine control module (ECM) from the body control module (BCM). 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 BCM also sends a voltage signal on the stop lamp switch circuit to the ECM.