Engine Control Module
WARNING: This page is about a different car, the 2007 GMC Envoy, 2007 Chevrolet TrailBlazer, and 2007 Buick Rainier. However, it is still accessible from the selected car via links, so may be relevant.
The engine control module (ECM) is the control center for the throttle actuator control (TAC) system. The ECM determines the driver intent and then calculates the appropriate throttle response. The ECM achieves throttle positioning by providing a pulse width modulated voltage to the TAC motor.