GM Corvette 1984-1996 Repair Guide

Vehicle Speed Sensor

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operation

The Vehicle Speed Sensor (VSS) is a pulse counter type input sensor which tells the PCM how fast the vehicle is being driven. An inductive sensor mounted in the tail housing of the transmission and a toothed reluctor wheel on the tail shaft. As the reluctor rotates, the teeth alternately interfere with the magnetic field of the sensor, creating an induced voltage pulse. The VSS produces an AC voltage signal increased with vehicle speed. The PCM processes this information, then sends a signal to the instrument panel, radio, chime module, and cruise control module.

testing

See Figure 1

  1. Visually check the connector, making sure it is connected properly and all of the terminals are straight, tight and free of corrosion.
  2.  
  3. Detach the VSS electrical connector, the measure the voltage between the terminals while the rear wheels of the vehicle are rotated. The sensor should generate a sine wave voltage signal that increases in amplitude and frequency as the vehicle speed increases. If the voltage measures less than 0.5 volts, the sensor is bad and must be replaced.
  4.  
  5. Check the resistance between the sensor terminals. It should measure between 1300-1950 ohms. If not within the range, the sensor is bad and must be replaced.
  6.  



Click image to see an enlarged view

Fig. Fig. 1: Vehicle Speed Sensor (VSS) circuit

  1. Check the resistance between the VSS and transmission case. The resistance should be more than 10 megaohm. If the resistance is not within specifications, the sensor is faulty.
  2.  
  3. If the resistance and voltage are within the proper ranges, check the sensor circuits for continuity.
  4.  
  5. If the sensor and circuits are OK, the PCM may be faulty.
  6.  

REMOVAL & INSTALLATION



See Figures 2 and 3

  1. Disconnect the negative battery cable.
  2.  
  3. Raise and safely support the vehicle.
  4.  
  5. Unplug the VSS electrical connector.
  6.  
  7. Unfasten the retainer bolt, the remove the sensor retainer, and spacer.
  8.  



Click image to see an enlarged view

Fig. Fig. 2: Remove the mounting bolt, the retainer and spacer

  1. Remove the VSS from the transmission case.
  2.  
  3. If necessary, remove the O-ring seal and the speedometer driven gear from the sensor.
  4.  



Click image to see an enlarged view

Fig. Fig. 3: Exploded view of the O-ring, gear and sensor

  1. Installation is the reverse of the removal procedure. Tighten the mounting bolt to 89 inch lbs. (10 Nm).
  2.  

 
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