Head Up Display (HUD) Description and Operation: Speedometer
WARNING: This page is about a different car, the 2003 Pontiac Aztek and 2003 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
The speedometer is shown on the HUD as a 3-digit display. The HUD speedometer is capable of displaying up to 120 mph. The HUD receives a class 2 message from the powertrain control module (PCM) indicating vehicle speed. If the class 2 message from the PCM is invalid the HUD will use a class 2 message from the EBCM instead.