GM Full Size Vans 1987-1997 Repair Guide

Vehicle Speed Sensor (VSS)

Print

OPERATION



The vehicle speed sensor is sometimes located behind the speedometer or more commonly on the transmission. It sends a pulsing voltage signal to the ECM, which the ECM converts to vehicle speed. This sensor mainly controls the operation of the Torque Convertor Clutch (TCC) system, shift light and cruise control.

TESTING



See Figure 1

  1. Backprobe the VSS terminals with a high impedance voltmeter (set at the AC voltage scale).
  2.  
  3. Safely raise and support the entire vehicle using jackstands. Make absolutely sure the vehicle is secure.
  4.  
  5. Start the vehicle and place it in gear.
  6.  
  7. Verify that the VSS voltage increases as the speed increases.
  8.  
  9. If the VSS voltage is not as specified the VSS may be faulty.
  10.  



Click image to see an enlarged view

Fig. Fig. 1: Vehicle Speed Sensor (VSS) wiring diagram

REMOVAL & INSTALLATION



Speedometer Mounted
  1. Disconnect the negative battery cable.
  2.  
  3. Remove the instrument cluster.
  4.  
  5. Remove the screws securing the sensor assembly.
  6.  
  7. Installation is the reverse of removal.
  8.  

Transmission Mounted
  1. Raise and safely support the vehicle.
  2.  
  3. Unplug the electrical connector.
  4.  
  5. Disconnect the speedometer cable from the sensor.
  6.  
  7. Remove the sensor from the transmission.
  8.  
  9. Installation is the reverse of removal.
  10.  

 
label.common.footer.alt.autozoneLogo