Principles of Operation: Gauges: Speedometer
WARNING: This page is about a different car, the 2005 Ford Pickup. 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 which originates in the ABS module and is transmitted to the PCM over the communication network. The PCM monitors the VSS input and sends it to the instrument cluster over the communication network. With the VSS input, the instrument cluster provides the speedometer with a corresponding pointer movement.