Circuit/System Description
WARNING: This page is about a different car, the 2010 Chevrolet Malibu. However, it is still accessible from the selected car via links, so may be relevant.
The power steering control module (PSCM) receives a power mode message from the body control module (BCM) via a serial data circuit. When a power mode ON message is received, the PSCM compares it to the state of its igniting voltage circuit.