Circuit/System Description (With JL4)
WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The body control module (BCM) sends a serial data message when the brake pedal is applied. The electronic brake control module (EBCM) compares the brake pressure sensor values to ensure they agree with the brake pedal applied signal.