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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 772 (Anti-Lock Brake System) >> Diagnostic Information & Procedures >> DTC C0235: Rear Wheel Speed Signal Circuit Open; C0236: Rear Wheel Speed Signal Circuit Missing; C0237: Rear Wheel Speed Signal Erratic; P1504: Vehicle Speed Output Circuit >> Test Description

Test Description

WARNING: This page is about a different car, the 2002 GMC Safari and 2002 Chevrolet Astro. 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 for a voltage signal from the PCM.
  2. 4)  - This step tests for a missing or erratic vehicle speed signal from the PCM. An assistant may be required to perform this test.
DTC C0235-C0237 Or P1504 Diagnosis

Step Action Values Yes No
1 Did you perform the ABS Diagnostic System Check? - Go to Step 2  Go to Diagnostic System Check - ABS 
2
  1. 1) Use a scan tool in order to clear the DTCs.
  2. 2) Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC set?		 - Go to Step 3  Diagnostic Aids
3
  1. 1) Turn OFF the ignition.
  2. 2) Disconnect from the EBCM, the harness connector containing the vehicle speed signal circuit.
  3. 3) Turn ON the ignition.
  4. 4) Use a DMM in order to measure the DC voltage between the vehicle speed signal circuit and a good ground.
Does the voltage measure greater than the specified value?		 10 Volts Go to Step 4  Go to Step 7 
4
  1. 1) Raise and support the vehicle.
  2. 2) Place the transmission in neutral (N)
  3. 3) Set up the DMM in order to measure the DC voltage between the vehicle speed signal circuit and a good ground.
  4. 4) Spin the rear wheels as fast as possible by hand for at least 30 seconds and while ensuring the driveshaft is rotating, observe the DMM.
Does the voltage measure within the specified range the entire time the driveshaft is rotating?		 5-7Volts Go to Step 5  Go to Step 7 
5 Inspect for poor connections at the harness connector of the EBCM. Refer to TESTING FOR INTERMITTENT & POOR CONNECTIONS  and  CONNECTOR REPAIRS  . Did you find and correct the condition? - Go to Step 10  Go to Step 6 
6 Important: Following EBCM replacement, use the scan tool to perform the Tire Size Calibration procedure. Replace the EBCM. Refer to ELECTRONIC BRAKE CONTROL MODULE (EBCM) REPLACEMENT . Did you complete the replacement? - Go to Step 10  -
7 Test the vehicle speed signal circuit for an open, a short to ground or a short to voltage. Refer to CIRCUIT TESTING  and  WIRING REPAIRS  . Did you find and correct the condition? - Go to Step 10  Go to Step 8 
8 Inspect for poor connections at the harness connector of the PCM. Refer to TESTING FOR INTERMITTENT & POOR CONNECTIONS  and  CONNECTOR REPAIRS  . Did you find and correct the condition? - Go to Step 10  Go to Step 9 
9 Important: Perform the setup procedure for the PCM. Replace the PCM. Refer to POWERTRAIN CONTROL MODULE  . Did you complete replacement? - Go to Step 10  -
10
  1. 1) Use the scan tool in order to clear the DTC.
  2. 2) Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?		 - Go to Step 3  System OK
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