GM Grand Am/Achieva/Calais/Skylark/Somerset 1985-98

Vehicle Speed Sensor (VSS)

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OPERATION



The VSS is located on the transmission and sends a pulsing voltage signal to the ECM which is converted to miles per hour. This sensor mainly controls the operation of the TCC system, shift light, cruise control and activation of the EGR system.

TESTING



  1. To test the VSS, backprobe the VSS terminals with a high impedance voltmeter (set to the AC voltage scale).
  2.  
  3. Safely raise the entire vehicle using jackstands, so the wheels can rotate freely. Make absolutely sure the vehicle is stable.
  4.  


CAUTION
Do not perform this procedure in a closed area. If the vehicle were to fall from the jackstands during the procedure, it could travel on its own, possibly causing severe bodily injury, as well as property damage.

  1. Start the vehicle, and place it in gear.
  2.  
  3. Verify that the VSS voltage increases as the drive speed increases.
  4.  
  5. If the VSS does not produce any AC voltage, or the voltage does not change according to vehicle speed, it can be considered faulty.
  6.  

REMOVAL & INSTALLATION



See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: The VSS is usually located in the right rear of the engine compartment-2.3L engine

  1. Disconnect the negative battery cable.
  2.  
  3. Raise and safely support the vehicle.
  4.  
  5. Detach the VSS lead from the transaxle.
  6.  
  7. If necessary, unfasten the governor housing bolts, then remove the housing.
  8.  
  9. Unfasten the bolt or screw and retainer, then remove the VSS assembly from the vehicle. Remove and discard the O-ring.
  10.  

To install:
  1. Lubricate a new O-ring with sychromesh transaxle fluid part no. 12345349 or equivalent, then install on the sensor.
  2.  
  3. Install the VSS assembly, then secure with the retainer and bolt/screw.
  4.  
  5. If removed, install the governor housing and secure with the retaining bolts.
  6.  
  7. Attach the VSS lead to the transaxle.
  8.  
  9. Carefully lower the vehicle.
  10.  
  11. Connect the negative battery cable.
  12.  

 
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