Circuit/System Description
WARNING: This page is about a different car, the 2009 Saturn Outlook, 2009 GMC Acadia, 2009 Chevrolet Traverse, and 2009 Buick Enclave. However, it is still accessible from the selected car via links, so may be relevant.
When a cruise control function switch is activated, the body control module (BCM) detects a predetermined voltage signal. The BCM sends a serial data message to the engine control module (ECM) indicating the function that has been requested.