Circuit/System Description
WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
The vehicle speed signal circuit is an input to the throttle actuator control (TAC) module from the powertrain control module (PCM). The TAC module uses the vehicle speed signal from the PCM in order to determine the vehicle speed. The TAC module then sends a serial data message to the PCM indicating the vehicle speed that the TAC module has detected.