Circuit/System Description
WARNING: This page is about a different car, the 2008 Buick Lucerne. However, it is still accessible from the selected car via links, so may be relevant.
The stop lamp switch signal circuit is a direct hardwire input from the body control module (BCM) to the powertrain control module (PCM) and the throttle actuator control (TAC) module. The modules monitor the stop lamp switch signal circuit to detect when the brake pedal has been applied. When the brake pedal is applied, the BCM sends a serial data message to the modules and also a voltage signal on the stop lamp switch signal circuit indicating that the brake pedal has been applied.