Speedometer Head: Description and Operation

The vehicle is equipped with electronically driven speedometer and odometer assemblies. A signal is sent from a transmission-mounted vehicle speed sensor to the speedometer circuitry through the wiring harness.

The speedometer has two main parts: the indicator head and the speedometer drive cable. When the speedometer fails to indicate speed or mileage, the cable or housing is probably broken.

CIRCUIT OPERATION
The speedometer receives its information across the CCD Bus from the Body Control Module (BCM). Information on vehicle speed is transmitted from the Powertrain Control Module (PCM) across the CCD Bus to the BCM.

The PCM receives its information on vehicle speed on the G7 circuit from the Transmission Control Module (TCM).

The BCM calculates the position of the speedometer pointer based on the input from the PCM and adjusts the position of the gauge pointer as necessary. This signal is sent over the CCD Bus to the instrument cluster.