Circuit/System Description
WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The starter generator control module (SGCM) provides a solenoid enable circuit to the hill hold solenoid relay. The relay provides voltage circuits to the hill hold solenoid valves (HHV). The SGCM controls the HHV through a pulse width modulated low side driver circuit, and converts electrical inputs into a mechanical valve action to trap the brake fluid under pressure from the master cylinder to the front brakes, and assist the driver as necessary for vehicle roll back control.