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Test Description

WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

  1. 3:  This step tests the ability of the VSS to produce an AC voltage. This step also verifies the integrity of the wiring to the PCM.
  2. 4:  This step tests the VSS circuit for correct resistance.
DTC P0502 (3.4L)

Step Action Value(s) Yes No
1 Did you perform the Diagnostic System Check - Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls in Engine Controls - 3.4L
2
  1. Install a scan tool.
  2. Turn ON the ignition switch with the engine OFF.
    3. IMPORTANT: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. Using the Clear DTC Information function will erase the stored Freeze Frame and Failure Records from the PCM.
  3. Record the Freeze Frame and Failure Records.
  4. Clear the DTCs.
    5. NOTE: Support the lower control arms in the normal horizontal position in order to avoid damage to the drive axles. Do not operate the vehicle in gear with the wheels hanging down at full travel.
  5. Raise and support the drive wheels.
  6. Start and idle the engine.
  7. Place the transmission in DRIVE.
  8. Monitor Transmission OSS on the scan tool.
  9. With the drive wheels rotating, increase and decrease the throttle position.
Does the Transmission OSS RPM increase when wheel speed increases?		 - Go to Intermittent Conditions in Engine Controls - 3.4L Go to Step 3 
3 
  1. Turn OFF the ignition.
  2. Disconnect the PCM connector C1.
  3. Using the J 35616  GM terminal test kit, connect the DMM between the VSS high signal and low signal circuits of the PCM harness connector.
  4. Select AC volts on the DMM.
  5. Turn ON the ignition with the engine OFF.
  6. Place the range selector in a DRIVE range or NEUTRAL.
  7. Rotate the right front drive wheel by hand, while observing the DMM display.
Does the voltage measure greater than the specified value?		 0.4 V AC Go to Step 8  Go to Step 4 
4 
  1. Leave the DMM test leads connected between the VSS high signal and low signal circuits of the PCM harness connector.
  2. Select ohms on the DMM.
  3. Measure the resistance of the complete VSS circuit.
Is the circuit resistance within the specified range?		 1,650-3,180 ohm Go to Step 9  Go to Step 5 
5 Is the circuit resistance greater than the specified value? 3,180 ohm Go to Step 11  Go to Step 6 
6
  1. Leave the DMM test leads connected between the VSS high signal and low signal circuits of the PCM harness connector.
  2. Disconnect the VSS connector at the transmission.
  3. Test the high signal circuit and the low signal circuit of the VSS for a short together.

    Refer to Circuit Testing in Wiring Systems.

Are the signal and ground circuits shorted together?		 - Go to Step 7  Go to Step 14 
7 Repair the short between the high signal circuit and the low signal circuit.
Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 16  -
8 Test the high signal circuit of the VSS for a short to ground between the PCM and the VSS.
Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 16  Go to Step 15 
9
  1. Reconnect the C1 PCM connector.
  2. Select DC volts on the DMM.
  3. Using the J 35616  connect the DMM between the VSS high signal and low signal circuits of the VSS vehicle harness.
  4. Turn ON the ignition with the engine OFF.
Does the DMM display greater than the specified voltage?		 1.0 V Go to Step 10  Go to Step 13 
10 Repair the short to voltage in the high signal circuit.
Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 16  -
11 Test the high signal circuit of the VSS for an open between the PCM and the VSS.
Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 16  Go to Step 12 
12 Test the low signal circuit of the VSS for an open between the PCM and the VSS.
Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 16  Go to Step 14 
13
  1. Remove the VSS.

    Refer to Vehicle Speed Sensor (VSS) Replacement .

  2. Inspect the VSS and the transmission for the following:
    • Incorrect VSS
    • VSS damage
    • Excessive runout in the final drive carrier assembly
    • Excessive VSS to speed sensor rotor gap
    • Incorrect speed sensor rotor alignment
    • Speed sensor rotor damage
  3. Repair any of the above items as necessary.
Refer to Differential Carrier Inspection (FWD Only) Transmission Unit Repair Manual.Did you find and correct the condition?		 - Go to Step 16  Go to Step 14 
14 Replace the VSS.
Refer to Vehicle Speed Sensor (VSS) Replacement .
Did you complete the replacement?		 - Go to Step 16  -
15 Replace the PCM.
Refer to Powertrain Control Module (PCM) Replacement in Engine Controls - 3.4L
Did you complete the replacement?		 - Go to Step 16  -
16 Perform the following procedure in order to verify the repair:
  1. Select DTC.
  2. Select Clear DTC Information.
  3. Drive the vehicle.
  4. Ensure that the transmission OSS is 250 RPM or more for at least 2 seconds.
  5. Select Specific DTC.
  6. Enter DTC P0502.

Has the test run and passed?		 - Go to Step 17  Go to Step 2 
17 With a scan tool, observe the stored information, capture info and DTC info.
Does the scan tool display any DTCs that you have not diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 3.4L System OK
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