Principles of Operation: Gauges: Speedometer
WARNING: This page is about a different car, the 2005 Mercury Mountaineer and 2005 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.
The instrument cluster receives the vehicle speed sensor (VSS) signal from the PCM through the CAN circuits. The instrument cluster monitors the VSS input from the PCM and commands a corresponding movement of the speedometer pointer.