Circuit/System Description
WARNING: This page is about a different car, the 2007 Saturn Sky. 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 engine control module (ECM) to the transmission control module (TCM) and the body control module (BCM). The ECM monitors the stop lamp switch signal circuit in order to detect when the brake pedal has been applied. When the brake pedal is pressed, the BCM sends a serial data message to the ECM indicating that the brake pedal has been applied. The ECM sends a high voltage signal on the stop lamp switch signal circuit to the BCM. This DTC will set if the serial data message and the voltage signal on the stop lamp switch signal circuit do not match.