Envoy, Rainer, Trailblazer 2006-2007

Vehicle Speed Sensor

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Operation



The Vehicle Speed Sensor (VSS) assembly provides vehicle speed information to the transmission control module (TCM) and powertrain control module (PCM). The VSS assembly is a permanent magnet (PM) generator. The PM generator produces a pulsing AC voltage as rotor teeth on the transmission output shaft pass through the sensor's magnetic field. The AC voltage level and the number of pulses increase as the speed of the vehicle increases. Output voltage varies with speed from a minimum of 0.5 volts at 100 RPM to more than 100 volts at 8,000 RPM. The TCM and PCM converts the pulsing voltage to vehicle speed. The TCM and PCM uses the vehicle speed signal to determine shift timing and torque converter clutch (TCC) scheduling.

Removal & Installation



  1. Disconnect the negative battery cable.
  2.  
  3. Remove the harness connector.
  4.  
  5. Remove the bolt (2).
  6.  
  7. Remove the vehicle speed sensor (1).
  8.  
  9. Remove the O-ring seal (3).

    Click image to see an enlarged view

    Fig. Location of the vehicle speed sensor (1), bolt (2) and O-ring seal (3)

  10.  

To install:

  1. Install the O-ring seal (3) on the vehicle speed sensor (1).
  2.  
  3. Coat the O-ring seal (3) with a thin film of transmission fluid.
  4.  
  5. Install the vehicle speed sensor (1) into the transmission case.
  6.  
  7. Install the bolt (2) and tighten to 97 inch lbs. (11 Nm).
  8.  
  9. Connect the wiring harness electrical connector to the vehicle speed sensor.
  10.  
  11. Refill the fluid as required.
  12.  
  13. Connect the negative battery cable.
  14.  

Testing



4.2L Engine


Click image to see an enlarged view

Fig. Vehicle Speed Sensor (VSS) wiring schematic-4.2L engine

  1. Install a scan tool.
  2.  
  3. Turn ON the ignition, with the engine OFF.
    NOTE
    Before clearing the Diagnostic Trouble Code (DTC), use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the powertrain control module (PCM).

  4.  
  5. Record the DTC Freeze Frame and Failure Records.
  6.  
  7. Clear the DTC.
  8.  
  9. Raise and support the rear axle assembly.
  10.  
  11. Start the engine.
  12.  
  13. Place the transmission in any drive range.
  14.  
  15. With the drive wheels rotating, if the scan tool Transmission OSS parameter increases with the drive wheel speed, then test for intermittent conditions or poor connections. If an intermittent condition or poor connection does not exist, continue.
  16.  
  17. Turn OFF the ignition.
  18.  
  19. Disconnect the Powertrain Control Module (PCM) connector.
  20.  
  21. Using the Digital Multi-Meter (DMM) and the J-35616 GM Terminal Test Kit, measure the resistance of the Vehicle Speed Sensor (VSS) high signal and VSS low signal circuits at the PCM harness connector.
  22.  
  23. If the resistance does not measure within the specified range of 1377-3355 ohms (2WD) or 1420-2140 ohms (4WD), disconnect the engine wiring harness from the VSS and measure the resistance at the VSS harness connector at the same specified range. If the resistance does measure within the specified range, proceed to the next step.
  24.  
  25. Place the transmission in NEUTRAL.
  26.  
  27. Select AC volts.
  28.  
  29. Prevent one rear wheel from turning.
  30.  
  31. Rotate the other rear wheel by hand, ensuring that the driveshaft is turning.
  32.  
  33. If the voltage does not measure greater than 0.5V, remove the VSS and inspect for damage, misalignment, or wear. If the voltage does measure greater than 0.5V, proceed to the next step.
  34.  
  35. Measure the resistance from the high signal circuit of the VSS to ground, and if the resistance measures less than 50K ohms, test the high signal circuit and the low signal circuit of the VSS for a short-to-ground.
  36.  
  37. If the resistance measures greater than 50K ohms, proceed to the next step.
  38.  
  39. Remove the VSS.
  40.  
  41. Inspect the output shaft speed sensor rotor for damage or misalignment.
  42.  
  43. Inspect the case extension bushing for wear.
  44.  
  45. If no such condition exists, replace the VSS.
  46.  
  47. Perform the following procedure in order to verify the repair:
    1. Select DTC
    2.  
    3. Select Clear Info.
    4.  
    5. Operate the vehicle, so that the transmission output speed is greater than 250 RPM for 2 seconds.
    6.  
    7. Select Specific DTC
    8.  
    9. Enter DTC P0502.
    10.  
    11. If the test did not pass, start all over again at the first step.
    12.  

  48.  
  49. With the scan tool, observe the stored information, capture info, and DTC Info.
  50.  
  51. Check for any un-diagnosed DTCs.
  52.  

5.3L & 6.0L Engines

DTC P0722

Click image to see an enlarged view

Fig. Vehicle Speed Sensor (VSS) wiring schematic-5.3L and 6.0L engines


NOTE
Disable the traction control system when performing this step. When the ignition key is cycled to the OFF position and then cycled back ON, the traction control system defaults to ON.

  1. Install a scan tool.
  2.  
  3. Turn ON the ignition, with the engine OFF.
    NOTE
    Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the Transmission Control Module (TCM).

  4.  
  5. Record the Freeze Frame and Failure Records.
  6.  
  7. Clear the DTC.
  8.  
  9. Raise and support the rear axle assembly.
  10.  
  11. Start the engine.
  12.  
  13. Disable the traction control system.
  14.  
  15. Place the transmission in any drive range.
  16.  
  17. With the drive wheels rotating, if the scan tool Transmission OSS parameter increases with the drive wheel speed, then test for an intermittent condition or poor connection. If an intermittent condition or poor connection does not exist, continue.
  18.  
  19. Turn OFF the ignition.
  20.  
  21. Disconnect the engine wiring harness from the vehicle speed sensor (VSS).
  22.  
  23. Using the Digital Multi-Meter (DMM) and the J-35616 GM Terminal Test Kit, measure the resistance of the VSS. It should measure within 976-2354 ohms.
  24.  
  25. Measure the resistance from the high signal circuit of the VSS to ground. If the resistance measures greater than 50K ohms, then continue with the next step. If the resistance measures less than 50K ohms, then replace the VSS.
  26.  
  27. Place the transmission in NEUTRAL.
  28.  
  29. Select AC volts on the DMM.
  30.  
  31. Hold one rear wheel from turning and rotate the other wheel by hand.
  32.  
  33. Measure the AC voltage from high signal and low signal circuits of the VSS. If the voltage measures greater than 0.3V AC, then continue with the next step. If the voltage measures less than 0.3V AC, then replace the VSS.
  34.  
  35. Connect the engine wiring harness to the VSS.
  36.  
  37. Disconnect the TCM.
  38.  
  39. Measure the resistance of the VSS high signal and VSS low signal circuits at the TCM connector. If the resistance measures within 976-2354 ohms, then continue onto the next step. If the resistance measures greater than 2354 ohms, then test the high signal circuit and the low signal circuit of the VSS for an open. If it is not, test the high signal and low signal circuits of the VSS for a short together.
  40.  
  41. Measure the resistance from the high signal and low signal circuits of the VSS to ground. If the resistance measures less than 50K ohms, test the high signal circuit and low signal circuit of the VSS for a short-to-ground. If the resistance measures greater than 50K ohms, continue.
  42.  
  43. Connect the TCM.
  44.  
  45. Disconnect the engine wiring harness from the VSS.
  46.  
  47. Turn ON the ignition, with the engine OFF.
  48.  
  49. Test the high signal and low signal circuits of the VSS for a short-to-voltage. If there is a short-to-voltage, continue. If no such condition exists, replace TCM.
  50.  
  51. Perform the following procedure in order to verify the repair:
    1. Select DTC.
    2.  
    3. Select Clear Info.
    4.  
    5. Operate the vehicle so that the transmission output speed is 250 RPM or greater for 2 seconds or more.
    6.  
    7. Select Specific DTC.
    8.  
    9. Enter DTC P0722.
    10.  
    11. If the test did not pass, start all over again at the first step.
    12.  

  52.  
  53. With the scan tool, observe the stored information, capture info, and DTC Info.
  54.  
  55. Check to see if the scan tool displays any undiagnosed DTCs.
  56.  

 
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