Section 16 (Instrument Cluster): Speedometer: Operation

WARNING: This page is about a different car, the 2006 Dodge Sprinter. However, it is still accessible from the selected car via links, so may be relevant.

The speedometer gives an indication to the vehicle operator of the vehicle road speed. This gauge is controlled by the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the Controller Anti-lock Brake (CAB) over the Controller Area Network (CAN) data bus. The speedometer is an air core magnetic unit that receives battery current on the instrument cluster electronic circuit board when the instrument cluster detects that the ignition switch is in the On position. The cluster is programmed to move the gauge needle back to the low end of the scale after the ignition switch is turned to the Off position. The instrument cluster circuitry controls the gauge needle position and provides the following features:

Vehicle Speed Message - Each time the cluster receives a vehicle speed message from the CAB it will calculate the correct vehicle speed reading and position the gauge needle at that relative speed position on the gauge scale. The gauge needle will continue to be positioned at the actual vehicle speed position on the gauge scale until the ignition switch is turned to the Off position.
Communication Error - If the cluster fails to receive a speedometer message, it will hold the gauge needle at the last indication for about three seconds, or until the ignition switch is turned to the Off position, whichever occurs first. After three seconds, the gauge needle will return to the left end of the gauge scale.

The CAB continually monitors the four wheel speed sensors to determine the vehicle road speed. The CAB then sends the proper vehicle speed messages to the instrument cluster. For proper diagnosis of the wheel speed sensors, the CAB, the CAN data bus, or the electronic message inputs to the instrument cluster that control the speedometer, a diagnostic scan tool is required. Refer to BODY DIAGNOSTIC PROCEDURES .