S15/T15 Sonoma P/U 2WD L4-2.2L VIN 4 (1995)
Vehicle Speed Sensor: Description and Operation
Circuit Operation
The Vehicle Speed Sensor, mounted to the transmission, 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 transmission rotates. The Speed at which the transmission rotates is proportional to tile speed of the vehicle.
For PCM equipped vehicles, the A/C signal produced by the Vehicle Speed Sensor is amplified and converted to a square wave by the Vehicle Speed
Sensor Buffer. The square wave signal is supplied to the PCM, Cruise Control Module, EBCM, Transfer Case Control Module and Speedometer by the
Vehicle Speed Sensor Buffer. The Vehicle Speed Sensor Buffer produces the square wave by opening and closing internal solid state switches to ground.
For VCM equipped vehicles, the Vehicle Speed Sensor supplies a square wave directly to the VCM and the VCM supplies a signal to the Speedometer.
For PCM equipped vehicles, tile square wave to the PCM is at a rate of 2000 pulses per mile while the other components see a square wave at 4000
pulses per mile. The PCM, Cruise Control Module and Speedometer internally convert the number of pulses per mile per second to determine vehicle
speed. For VCM equipped vehicles. the VCM sends a square wave to the Speedometer at a rate of 4000 pulses per mile.
The Vehicle Speed Sensor Buffer is matched to the vehicle based on transmission, final drive ratio and tire size. It is important to ensure that the correct
Vehicle Speed Sensor buffer is installed in tile vehicle if replacement is necessary.
