Inspection and Verification

Auxiliary Brake System - Trailer Brake Control (TBC) Module

Inspection and Verification

NOTE: A trailer brake emulator tool is available to verify that the Trailer Brake Control (TBC) module and vehicle wiring are functioning correctly.

1. Verify the customer concern.

2. NOTE: The TBC system does not function with electric-over-hydraulic or surge trailer brake types.

Verify that the trailer brakes are electric-actuated drum type brakes.

3. Verify that the yellow ABS warning indicator shuts off after prove out. If the warning indicator operates correctly, proceed to the next step. If the warning indicator remains illuminated, GO to Antilock Brakes / Traction Control Systems to diagnose the warning indicator.

4. Verify the vehicle stoplamps operate correctly by applying and releasing the brake pedal with the ignition switch in the OFF position and the trailer disconnected. If the stoplamps do not operate correctly, refer to Lighting and Horns. If the vehicle stoplamps operate correctly, proceed to the next step.

5. Visually inspect for obvious signs of mechanical or electrical damage.

Visual Inspection Chart





6. If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.

7. NOTE: Make sure to use the latest scan tool software release.

If the cause is not visually evident, connect the scan tool to the Data Link Connector (DLC).

8. NOTE: The Vehicle Communication Module (VCM) LED prove out confirms power and ground from the DLC are provided to the VCM.

If the scan tool does not communicate with the VCM:

- check the VCM connection to the vehicle.

- check the scan tool connection to the VCM.

- refer to Information Bus, No Power To The Scan Tool, to diagnose no power to the scan tool.

9. If the scan tool does not communicate with the vehicle:
- verify the ignition key is in the ON position.

- verify the scan tool operation with a known good vehicle.

- refer to Information Bus to diagnose no response from the PCM.

10. Carry out the network test.
- If the scan tool responds with no communication for one or more modules, refer to Information Bus.

- If the network test passes, retrieve and record Continuous Memory Diagnostic Trouble Codes (CMDTCs).

11. Clear the CMDTCs and carry out the self-test diagnostics for the TBC module.

12. If the DTCs retrieved are related to the concern, go to the Trailer Brake Control (TBC) Module DTC Chart. For all other DTCs, refer to Body Control Systems. Trailer Brake Control (TBC) Module DTC Chart

13. If no DTCs related to the concern are retrieved, GO to Symptom Chart. Symptom Related Diagnostic Procedures