GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2005 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Brakes 🢒 Hydraulic Brakes 🢒 DTC C0163 or C0164

Circuit Description

The stop lamp switch input informs the electronic brake control module (EBCM) when the brake is pressed. The EBCM uses this input for Antilock Brake System (ABS) enhancement and HydroMax pump motor control.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • DTC C0163 Antilock Brake System (ABS)/Traction Control System (TCS) Brake Switch Circuit Low
    • DTC C0164 Antilock Brake System (ABS)/Traction Control System (TCS) Brake Switch Circuit High

Conditions for Running the DTC

C0163

The vehicle accelerates from 0 km/h (0 mph) to 37 km/h (23 mph).

C0164

The vehicle performs 3 consecutive stops from at least 37 km/h (23 mph) to 0 km/h (0 mph) during a single ignition cycle.

Conditions for Setting the DTC

The EBCM detects an open or shorted stop lamp switch or stop lamp switch circuit.

Action Taken When the DTC Sets

C0163

The EBCM stores an information-only DTC as a current DTC until the ignition is turned OFF or the EBCM detects an open stop lamp switch.

C0164

    • The service brake soon indicator turns ON.
    • A fast rate audible chime 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

Check wiring harness around heater box and right side engine clamp for signs of wear. Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Refer to Testing for Electrical Intermittents , Testing for Intermittent Conditions and Poor Connections , Wiring Repairs and Connector Repairs in Wiring Systems.

Step

Action

Yes

No

Schematic Reference: Brake Warning System Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
  1. Install a scan tool.
  2. Select the 4WAL 3 Sensor Data Display function.
  3. Observe the Brake Switch Status on the scan tool while pressing an releasing the brake.

Does the Brake Switch Status change from Off to On when the brake is pressed?

Go to Diagnostic Aids

Go to Step 3

3

Press and release the brake pedal while having an assistant observe the stop lamps.

Do the stop lamps turn ON and OFF properly?

Go to Step 4

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

4
  1. Turn the ignition OFF.
  2. Disconnect the electronic brake control module (EBCM) harness connector.
  3. Disconnect the stop lamp switch harness connector. Refer to Stop Lamp Switch Replacement in Lighting Systems.
  4. Test the stop lamp switch signal circuit for a short to ground or an open/high resistance between the EBCM and the stop lamp switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 7

Go to Step 5

5

Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 7

Go to Step 6

6

Replace the EBCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 7

--

7
  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