Circuit/System Description
WARNING: This page is about a different car, the 2008 Pontiac G5 and 2008 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.
The body control module (BCM) monitors the brake fluid level switch signal circuit and the park brake switch signal circuit. When either of these signal circuits are shorted to ground, the BCM sends a serial data message to the instrument panel cluster (IPC) requesting illumination of the Red Brake Warning indicator.