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Home >> GMC >> 2003 >> Jimmy 2D Utility, Part Time, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 137 (Antilock Brake System, Traction Control System & Stability Control System) >> Diagnostic Information and Procedures >> DTC C1277 or P0856 >> 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. 3:  Clear the DTC in order to verify that the fault is present.
  2. 4:  Measure the requested torque signal in order to determine if the signal has a valid duty cycle.
  3. 5:  Measure the requested torque signal in order to determine if the signal has a valid frequency.
  4. 11:  This vehicle is equipped with a PCM which uses an electrically erasable programmable read only memory (EEPROM). When replacing the PCM, the replacement PCM must be programmed.
DTC C1277 or P0856

Step Action Values Yes No
Schematic Reference: ABS Schematics 
Connector End View Reference: ABS Connector End Views  or Powertrain Control Module (PCM) Connector End Views in Engine Controls-5.7 L
1 Did you perform the ABS Diagnostic System Check? - Go to Step 2  Go to Diagnostic System Check - ABS 
2 Inspect the EBCM ground and PCM ground, making sure each ground is clean and torqued to the proper specification. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 13  Go to Step 3 
3 
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Use the scan tool in order to clear the DTCs in both the EBCM and PCM.
  4. Turn OFF the ignition.
  5. Start the engine.
Does the DTC reset as a current DTC?		 - Go to Step 4  Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
4 
  1. Turn OFF the ignition.
  2. Disconnect the EBCM harness connector.
  3. Install the J 39700 universal breakout box using the J 39700-300  cable adapter to the EBCM harness connector and the EBCM connector. See Special Tools and Equipment .
  4. Start the engine.
  5. Measure the DC duty cycle between the requested torque signal circuit and a good ground.
Is the duty cycle within the specified range?		 5-95% Go to Step 5  Go to Step 6 
5  Measure the DC Hz between the requested torque signal circuit and a good ground.
Does the frequency measure within the specified range?		 121-134 Hz Go to Step 8  Go to Step 6 
6
  1. Turn OFF the ignition.
  2. Disconnect the J 39700-300  cable adapter from the EBCM connector. See Special Tools and Equipment .
    3. IMPORTANT: Disconnecting the EBCM connector and turning ON the ignition could cause other modules to set loss of communication DTCs (Uxxxx). Once the EBCM is reconnected, the EBCM may set DTC C1298.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from the requested torque signal circuit to a good ground.
Does the voltage measure within the specified range?		 4-6 V Go to Step 10  Go to Step 7 
7
  1. Turn OFF the ignition.
  2. Disconnect the powertrain control module (PCM) harness connector.
  3. Test the requested torque signal circuit for the following conditions:
    • A short to voltage
    • A short to ground
Refer to Circuit Testing and Wiring Repairs in Wiring Systems.Did you find and correct the condition?		 - Go to Step 13  Go to Step 10 
8
  1. Turn OFF the ignition.
  2. Disconnect the powertrain control module (PCM) harness connector.
  3. Test the requested torque signal circuit for the following conditions:
    • An open
    • A high resistance
Refer to Circuit Testing and Wiring Repairs in Wiring Systems.Did you find and correct the condition?		 - Go to Step 13  Go to Step 9 
9 Inspect for poor connections the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 13  Go to Step 11 
10 Inspect for poor connections the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 13  Go to Step 12 
11 
IMPORTANT: The replacement PCM must be programmed.
Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement in Engine Controls - 5.7 L.Did you complete the repair?		 - Go to Step 13  -
12 Replace the EBCM. Refer to Electronic Brake Control Module Replacement .
Did you complete the repair?		 - Go to Step 13  -
13
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?		 - Go to Step 2  System OK
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