Circuit/System Description
WARNING: This page is about a different car, the 2008 GMC Yukon XL and 2008 Chevrolet Suburban. 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.