Instrument Panel Cluster (IPC) Description and Operation: Speedometer

WARNING: This page is about a different car, the 2003 Pontiac Sunfire and 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.

The IPC displays the vehicle speed based on the information from the BCM. The BCM receives a class 2 message from the PCM indicating the vehicle speed. The PCM calculates the vehicle speed based on the class 2 message indicating the wheel reference speed from the EBCM if:

The PCM detects a malfunction in the vehicle speed sensor circuit.
The IPC detects a loss of class 2 communications with the BCM.

The speedometer defaults to 0 km/h (0 mph) if the BCM detects a loss of class 2 communications with both the PCM and the EBCM.