GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 GMC T-Series Medium Duty Truck F6/F7/F8 🢒 DTC 🢒 DTC C0281 or C081

Circuit Description

The brake switch signal informs the EBCM when the brake is applied. The EBCM sends a 12 volt signal to the inverting driver module via the brake switch signal circuit. The inverting driver module opens or grounds the circuit based on brake switch input.

Conditions for Running the DTC

Either of the following conditions will cause the DTC to run:

    • The ignition is ON and the vehicle achieves at least 56 km/h (35 mph) before coming to a stop.
    • The ignition is ON and the vehicle experiences an antilock brake system (ABS) event lasting at least 1 second.

Conditions for Setting the DTC

The EBCM detects an open or shorted brake switch or brake switch circuit.

Action Taken When the DTC Sets
    • The EBCM disables the ABS.
    • The ABS 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 verifies that the inverting driver module is receiving adequate power and ground in order to power up.

    2.

  2. This step simulates the inverting driver module sending a brake ON signal to the EBCM. Exercise caution when removing the delicate circuit board.

    3.

  3. This step simulates the inverting driver module sending a brake OFF signal to the EBCM.

    4.

  4. This step tests the brake switch signal circuit for a short to voltage prior to checking for continuity. Measuring the resistance of a circuit that is shorted to voltage may damage the DMM.

Step

Action

Yes

No

Schematic Reference: Antilock Brake System Schematics

1

Did you perform the ABS Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - ABS

2

Observe the stop lamps while applying and releasing the brake.

Do the stop lamps operate normally?

Go to Step 3

Go to Stop Lamps Always On or Stop Lamps Inoperative in Lighting Systems

3
  1. Select the Hydraulic 4WAL 4 Sensor Data Display function.
  2. Observe the Brake Switch Status on the scan tool while applying and releasing the brake several times.

Does the Brake Switch Status toggle On and Off as the brake is applied and released?

Go to Diagnostic Aids

Go to Step 4

4
  1. Locate and access the inverting driver module.
  2. Backprobe the inverting driver module harness connector in order to connect a test lamp between the TCC brake switch signal circuit and a good ground. Refer to Probing Electrical Connectors in Wiring Systems.
  3. Apply the brake.

Does the test lamp illuminate?

Go to Step 5

Go to Step 9

5

Backprobe the inverting driver module harness connector in order to connect a test lamp between the ignition 1 voltage circuit and the ground circuit of the inverting driver module. Refer to Probing Electrical Connectors in Wiring Systems.

Does the test lamp illuminate?

Go to Step 6

Go to Step 12

6

Observe the Brake Switch Status on the scan tool.

Does the scan tool always display Brake Switch Status Off?

Go to Step 7

Go to Step 8

7

  1. Turn OFF the ignition.
  2. Remove the circuit board from the inverting driver module.
  3. Turn ON the ignition.
  4. Observe the Brake Switch Status on the scan tool.

Does the scan tool display On?

Go to Step 15

Go to Step 10

8

  1. Use a test lamp connected to a good ground in order to backprobe the brake switch signal circuit at the inverting driver module harness connector. Refer to Probing Electrical Connectors in Wiring Systems.
  2. Observe the Brake Switch Status on the scan tool.

Does the scan tool display Off?

Go to Step 13

Go to Step 11

9

Repair the open in the TCC brake switch signal circuit between the inverting driver module and the nearest splice connection. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 17

--

10
  1. Turn OFF the ignition.
  2. Disconnect the 24-way EBCM harness connector.
  3. Test the brake switch signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 14

11

  1. Turn OFF the ignition.
  2. Disconnect the 24-way EBCM harness connector.
  3. Turn ON the ignition.
  4. Test the brake switch signal circuit for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 14

12

Test the ignition 1 voltage circuit and the ground circuit of the inverting driver module for an open. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

--

13

Inspect for poor connections at the harness connector of the inverting driver module. 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 17

Go to Step 15

14

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 17

Go to Step 16

15

Replace the inverting driver module.

Did you complete the replacement?

Go to Step 17

--

16

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

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

Did you complete the replacement?

Go to Step 17

--

17
  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