Instrument Cluster Description and Operation: Speedometer

The IPC displays the vehicle speed as determined by the ECM. The IPC calculates the mileage based on the serial data vehicle speed information from the ECM. Vehicle speed is sent from the transmission control module (TCM) as trans output rotations and received by the ECM and turned into vehicle speed. The ECM transmits vehicle speed to the body control module (BCM) which in turn transmits the vehicle speed to the IPC via the serial data circuit. The speedometer defaults to 0 km/h (0 mph) if:

• The IPC detects a loss of serial data communications with the BCM.
• The BCM detects a loss of serial data communications with the ECM.