Speedometer and Odometer

The Vehicle Speed Sensor (VSS) generates a signal that indicates the vehicle speed. The signal is processed by the solid state Powertrain Control Module (PCM) to supply inputs to the speedometer and the odometer.

The vehicle speed sensor is mounted in the transaxle, and generates an AC voltage signal with a frequency proportional to vehicle speed. The PCM takes the voltage pulses from the sensor and uses them to close a solid state output sensor and uses them to close a solid state output switch. The output terminal is switched to ground at a rate that is proportional to vehicle speed. The speedometer and odometer are switched at the same frequency that the sensor generates.

The speedometer and odometer are operated by a circuit board in the cluster. This circuit board converts the pulses received from the PCM into a control signal for the vacuum fluorescent displays.