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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 967 (Automatic Transmission - 4L60-E/4L65-E Diagnosis (P0218 To P0785)) >> Diagnosis >> DTC P0502 >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra and 2004 Chevrolet 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 VSS assembly circuit.
  2. 4:  This step tests the integrity of the VSS assembly.
DTC P0502

Step Action Values 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 - 4.3L or Diagnostic System Check - Engine Controls in Engine Controls - 4.8L, 5.3L and 6.0L
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 Intermittent Conditions in Engine Controls - 4.3L or Intermittent Conditions in Engine Controls - 4.8L, 5.3L and 6.0L 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 the VSS high signal and VSS low signal circuits at the PCM harness connector.
Does the resistance measure within the specified range?		 1,377-3,355 Ω (2WD)
976-2,354 Ω (4WD)		 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 from the high signal circuit of the VSS to ground.
Does the resistance measure greater than the specified value?		 50 K Ω Go to Step 6  Go to Step 9 
6
  1. Connect the PCM.
  2. Disconnect the engine wiring harness from the VSS assembly.
  3. Turn ON the ignition, with the engine OFF.
  4. Test the high circuit of the VSS assembly for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 14 
7
  1. Disconnect the engine wiring harness from the VSS assembly.
  2. Measure the resistance of the VSS assembly.
Does the resistance measure within the specified range?		 1,377-3,355 Ω (2WD)
976-2,354 Ω (4WD)		 Go to Step 8  Go to Step 13 
8 Was the resistance measured in step 3 greater than the specified value? 3,355 Ω (2WD)
2,354 Ω (4WD)		 Go to Step 10  Go to Step 11 
9 Test the high circuit of the VSS assembly for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 15  -
10
  1. Test the high circuit of the VSS assembly for an open.
  2. Test the low circuit of the VSS assembly for an open. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 15  -
11 Test the high circuit and the low circuit of the VSS assembly for a short together. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 15  -
12
  1. Remove the VSS 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 VSS assembly before replacing. There are 2 transfer case speed sensors located near the VSS assembly. Refer to the wire colors on the schematic to identify the VSS assembly.
Replace the VSS assembly. Refer to Vehicle Speed Sensor (VSS) Replacement .Did you complete the replacement?		 - Go to Step 15  -
14 Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement in Engine Controls - 4.3L or Powertrain Control Module (PCM) Replacement in Engine Controls - 4.8L, 5.3L and 6.0L.
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 in Engine Controls - 4.3L or Diagnostic Trouble Code (DTC) List in Engine Controls - 4.8L, 5.3L and 6.0L System OK
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