Instrument Panel Cluster (IPC) Description and Operation: Speedometer
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2003 GMC Savana Special, 2003 GMC Savana Camper Special, 2003 GMC Savana, 2003 Chevrolet RV Cutaway, and 2003 Chevrolet Cutaway. 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 PCM. The PCM calculates the vehicle speed from the vehicle speed sensor (VSS) circuit. The IPC receives a class 2 message from the PCM indicating the vehicle speed.
The PCM also calculates the vehicle speed based on the wheel reference vehicle speed class 2 message from the EBCM. The PCM uses the vehicle speed information from the EBCM as a backup. The IPC displays the vehicle speed information from the EBCM when the PCM detects a malfunction in the vehicle speed sensor circuit.
The speedometer defaults to 0 km/h (0 mph) if the IPC detects a loss of class 2 communications with both the PCM and the EBCM.