Vehicle Speed Sensor: Description and Operation

The Vehicle Speed Sensor, mounted to the Transaxle, produces an AC signal in the form of a sine wave. The frequency of this sine wave is proportional to the speed at which the Transaxle rotates. The speed at which the Transaxle rotates is proportional to the speed of the vehicle.
The Vehicle Speed Sensor supplies a square wave directly to the PCM and the PCM supplies a signal to the Speedometer.
The PCM sends a square wave to the Speedometer at a rate of 4000 pulses per mile.