Speedometer Head: Description and Operation

SPEEDOMETER

The instrument panel cluster (IPC) displays the vehicle speed based on the information from the vehicle speed sensor. The IPC receives a GMLAN message from the body control module (BCM) indicating the vehicle speed. The IPC calculates the vehicle speed based on the GMLAN message indicating the wheel reference speed from the BCM if:
- The powertrain control module (PCM) or the engine control module (ECM) detects a malfunction in the vehicle speed sensor circuit.
- The IPC detects a loss of GMLAN communications with the BCM.

The speedometer defaults to 0 km/h (0 mph) if the IPC detects a loss of GMLAN communications with the BCM.