GM Service Manual Online
For 1990-2009 cars only

The vehicle speed sensor (VSS) mounts to the automatic or manual transmission assembly.

The VSS uses a permanent magnetic generator in order to produce an alternating current (AC) signal.

The frequency of the AC signal is proportional to the speed at which the transmission output shaft rotates.

The speed at which the transmission output shaft rotates is proportional to the speed of the vehicle.

The AC signal is produced in the following manner:

  1. The AC signal is produced by the VSS.
  2. The VSS is amplified.
  3. The VSS is converted by the PCM/VCM.
  4. The signal is supplied to the cruise control module and to the speedometer by the PCM/VCM.

The following components receive a signal which pulses at a rate of 4,000 times per mile:

These components also internally convert the number of pulses per mile in order to determine the vehicle speed:

    • The PCM/VCM
    • The cruise control module
    • The speedometer

For replacement procedures, refer to Vehicle Speed Sensor in Transmission/Transaxle.