Circuit/System Description
WARNING: This page is about a different car, the 2016 Chevrolet Trax and 2016 Buick Encore. However, it is still accessible from the selected car via links, so may be relevant.
The body control module (BCM) activates the ignition circuit, when the ignition key is in ACC, ON or START. The ignition circuit wakes up the devices for serial data bus communication.