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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1508 (Automatic Transmission, 4L60-E/4L65-E Diagnosis (DTC P0218 To DTC P2761)) >> Diagnosis >> DTC P0502 >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 Chevrolet Corvette. 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. 2:  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.
  2. 3:  This step tests the VSS assembly.
  3. 5:  This step tests the integrity of the VSS assembly.
DTC P0502

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
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 Freeze Frame and Failure Records.
  4. Clear the DTC.
  5. Raise and support the rear axle assembly.
  6. Start the engine.
  7. Disable the traction control system.
  8. 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 Go to Step 3 
3 
  1. Turn OFF the ignition.
  2. Disconnect the engine wiring harness from the VSS assembly.
  3. Using the DMM and the J 35616  GM Terminal Test Kit, measure the resistance of the VSS assembly.
Does the resistance measure within the specified range?		 976-2354 Ω Go to Step 4  Go to Step 13 
4 Measure the resistance from terminal B of the VSS assembly to ground.
Does the resistance measure greater than the specified range?		 50 K Ω Go to Step 5  Go to Step 13 
5 
  1. Place the transmission in NEUTRAL.
  2. Select AC volts on the DMM.
  3. Hold one rear wheel from turning.
  4. Rotate the other wheel by hand.
  5. Measure the AC voltage from terminal A and B of the VSS assembly.
Does the voltage measure greater than the specified value?		 0.3 V AC Go to Step 6  Go to Step 13 
6
  1. Reconnect the engine wiring harness to the VSS assembly.
  2. Disconnect the PCM connector C2.
  3. Measure the resistance between PCM connector terminals C2-20 and C2-21.
Does the resistance measure within the specified range?		 976-2354 Ω Go to Step 7  Go to Step 8 
7 Measure the resistance from terminal C2-21 to ground.
Does the resistance measure greater than the specified range?		 50 K Ω Go to Step 9  Go to Step 10 
8 Does the resistance measure greater than the specified value? 2354 Ω Go to Step 11  Go to Step 12 
9
  1. Reconnect the PCM connector C2.
  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 power.
  5. Test the low circuit of the VSS assembly for a short to power.

    Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?		 - Go to Step 15  Go to Step 14 
10
  1. Test the high circuit of the VSS assembly for a short to ground.
  2. Test the low 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  -
11
  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  -
12 Test the high circuit and the ground 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  -
13 Replace the VSS assembly.
Refer to Vehicle Speed Sensor (VSS) Replacement in Rear Drive Axle.
Did you complete the replacement?		 - Go to Step 15  -
14 Replace the PCM.
Refer to Powertrain Control Module (PCM) Replacement in Engine Controls.
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 500 RPM for 3 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 System OK
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