GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 TrailBlazer - 2WD 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC C0287, P1644, or P1689

Circuit Description

The EBCM supplies 5 VDC to the powertrain control module (PCM) on the delivered torque signal circuit. The PCM toggles this voltage to ground in order to create the delivered torque signal at the EBCM. A signal with a frequency of 128 Hz +/- 5 percent and a duty cycle of 25-95 percent is a valid delivered torque signal. The percentage of duty cycle is proportionate to the percentage of delivered torque.

Conditions for Running the DTC
    • The ignition is ON.
    • The engine is running at a speed greater than 450 RPM for 1 second.

Conditions for Setting the DTC

C0287

The EBCM receives an invalid delivered torque signal for 300 milliseconds.

P1689

The PCM detects the delivered torque signal voltage as being less than 4.75 volts or greater than 5.25 volts.

Action Taken When the DTC Sets
    • The EBCM disables the TCS.
    • The traction off indicator turns ON.

Conditions for Clearing the DTC

The conditions for setting the DTC are no longer present and you use the scan tool Clear DTCs function.

Diagnostic Aids

Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Refer to the following:

    •  Testing for Electrical Intermittents
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs
    •  Connector Repairs

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step tests for voltage supplied to the PCM from the EBCM.

    2.

  2. The PCM may be damaged if the delivered torque signal circuit is shorted to voltage.

Step

Action

Values

Yes

No

Schematic Reference: Antilock Brake System Schematics

Connector End View Reference: Antilock Brake System Connector End Views or Powertrain Control Module Connector End Views in Engine Controls - 4.8L, 5.3L and 6.0L

1

Did you perform the ABS Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - ABS

2
  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 set?

--

Go to Step 3

Go to Diagnostic Aids

3

  1. Turn OFF the ignition.
  2. Disconnect from the PCM, the harness connector containing the delivered torque signal circuit.
  3. Turn ON the ignition.
  4. Use a DMM in order to measure the voltage between the delivered torque signal circuit and a good ground.

Does the voltage measure within the specified range?

4.75-5.25 V

Go to Step 5

Go to Step 4

4

Test the delivered torque signal circuit for an open, a short to voltage or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 7

5
  1. Turn OFF the ignition.
  2. Reconnect the PCM harness connector.
  3. Start the engine.
  4. Select the Traction Assist Data Display on the scan tool.
  5. Observe the Delivered Torque parameter on the scan tool.

Is the duty cycle of the delivered torque signal is within the specified range?

25-95%

Go to Step 6

Go to Step 9

6
  1. Turn OFF the ignition.
  2. Install a J 39700 100-pin breakout box using a J 39700-325 breakout box adaptor. Install the equipment between the EBCM and the EBCM harness connector.
  3. Start the engine.
  4. Use a DMM in order to measure the Hz frequency of the delivered torque signal.

Does the frequency of the delivered torque signal measure within the specified range?

121-134 Hz

Go to Step 7

Go to Step 9

7
  1. Turn OFF the ignition.
  2. Inspect for poor connections at 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 12

Go to Step 8

8

Important: Following EBCM replacement, use the scan tool to perform the Tire Size Calibration procedure.

Replace the EBCM. Refer to Electronic Brake Control Module Replacement .

Did you complete the replacement?

--

Go to Step 12

--

9

  1. Turn ON the ignition.
  2. Test the delivered torque signal circuit 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 12

Go to Step 10

10

Inspect for poor connections at 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 12

Go to Step 11

11

Important: Perform the setup procedure for the PCM.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 4.8L, 5.3L, and 6.0L.

Did you complete the replacement?

--

Go to Step 12

--

12
  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 3

System OK