Speedometer

The speedometer is an analog gauge that is located in the instrument cluster. The VCM/PCM sends vehicle speed pulses to the instrument cluster on a designated circuit.

The speedometer system consists of the instrument cluster, vehicle speed sensor (VSS), PCM/VCM and related wiring. Repairs to the instrument cluster can only be performed by an authorized instrument cluster service center.

The PCM/VCM converts the analog output from the vehicle speed sensor to a digital signal containing 4,000 pulses per mile (PPM) for the instrument cluster. The PCM/VCM is matched to the final drive and tire size of each vehicle. If the final drive or tire size is changed for any reason, the PCM/VCM must be updated in order to match the new final drive or tire size. If not, the signal will not be accurate for proper speedometer/odometer operation. An incorrect signal can affect the antilock brakes and the cruise control systems.

The VSS is a permanent magnet signal generator that sends an analog signal proportional to the propeller shaft speed to the PCM/VCM. The VSS mounts to the transmission tailshaft extension housing on 2-wheel drive models and the transfer case output shaft housing on 4-wheel drive models.