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Test Description

WARNING: This page is about a different car, the 2006 GMC Sierra, 2006 GMC Cab & Chassis Sierra, 2006 Chevrolet Silverado, and 2006 Chevrolet Cab & Chassis Silverado. 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 OSS/VSS assembly circuit.
  2. 4:  This step tests the integrity of the OSS assembly.
DTC P0502

Step Action Value Yes No
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
    3. IMPORTANT: 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 PCM.
  3. Record the DTC Freeze Frame and Failure Records.
  4. Clear the DTC.
  5. Raise and support the rear axle assembly.
  6. Start the engine.
  7. Place the transmission in any drive range.
With the drive wheels rotating, does the scan tool Transmission OSS increase with the drive wheel speed?		 - Go to Testing for Intermittent Conditions and Poor Connections Go to Step 3 
3
  1. Turn OFF the ignition.
  2. Disconnect the PCM connector C2.
  3. Using the DMM and the J 35616  GM terminal test kit, measure the resistance between VSS high signal and VSS low signal.
Does the resistance measure within the specified range?		 1,420-2,140 Ω Go to Step 4  Go to Step 7 
4
  1. Place the transmission in NEUTRAL.
  2. Select AC volts.
  3. Prevent one rear wheel from turning.
  4. Rotate the other rear wheel by hand, ensuring that the driveshaft is turning.
Does the voltage measure greater than the specified value?		 0.5 V Go to Step 5  Go to Step 12 
5 Measure the resistance between the VSS high signal and ground.
Does the resistance measure greater than the specified value?		 10 M Ω Go to Step 6  Go to Step 9 
6
  1. Connect the PCM connector C2.
  2. Disconnect the engine wiring harness from the OSS assembly.
  3. Turn ON the ignition, with the engine OFF.
  4. Test both the high signal circuit and the low signal circuit of the OSS assembly for a short to voltage. Refer to Testing for a Short to Voltage and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 15  Go to Step 14 
7
  1. Disconnect the engine wiring harness from the OSS assembly.
  2. Measure the resistance of the OSS assembly.
Does the resistance measure within the specified range?		 1,420-2,140 Ω Go to Step 8  Go to Step 13 
8 Was the resistance measured in Step 3 greater than the specified value? 2,140 Ω Go to Step 10  Go to Step 11 
9 Test the high signal circuit of the OSS assembly for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 15  -
10
  1. Test the high signal circuit of the OSS assembly for an open.
  2. Test the low signal circuit of the OSS assembly for an open.
Refer to Testing for Continuity and Wiring Repairs .Did you find and correct the condition?		 - Go to Step 15  -
11 Test the high signal circuit and the low signal circuit of the OSS assembly for a short together. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 15  -
12
  1. Remove the OSS assembly.
  2. Inspect the output shaft speed sensor rotor for damage or misalignment.
  3. Inspect the case extension bushing for wear.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 13 
13
IMPORTANT: For vehicles equipped with an active transfer case, identify the OSS assembly before replacing. There are 2 transfer case speed sensors located near the OSS assembly. Refer to the wire colors on the schematic to identify the OSS assembly.
Replace the OSS assembly. Refer to Input Shaft Speed Sensor Replacement or Output Shaft Speed Sensor Replacement .Did you complete the replacement?		 - Go to Step 15  -
14 Replace the PCM. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?		 - Go to Step 15  -
15 Perform the following procedure in order to verify the repair:
  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle, so that the transmission output speed is greater than 250 RPM for 2 seconds.
  4. Select Specific DTC.
  5. Enter DTC P0502.

Has the test run and passed?		 - Go to Step 16  Go to Step 2 
16 With the 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 - Vehicle System OK
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