Circuit/System Description
WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The PSCM monitors vehicle speed validity message from the engine control module (ECM) via the serial data circuit. The power steering control module (PSCM) uses this vehicle speed message, along with the torque sensor and motor rotational sensor inputs, to determine the desired amount of steering assist.