Instrument Cluster Description and Operation: Speedometer

The IPC displays the vehicle speed based on the information from the BCM. The ECM calculates the vehicle speed based on the vehicle speed sensor (VSS) input. The ECM sends a serial data message to the BCM indicating the vehicle speed. The BCM sends a serial data message to the IPC indicating the vehicle speed.

The speedometer defaults to 0 km/h (0 mph) when any of the following occur:

• The EBCM detects a malfunction in the vehicle speed sensor circuit.
• The PCM detects a loss of serial data communications with the EBCM.
• The BCM detects a loss of serial data communications with the PCM.
• The IPC detects a loss of serial data communications with the BCM.