Trailer Brake Controls

DTC C0561 (Gasoline With LY6, or Diesel)

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors
DTC C0561 F0
- System Disabled Information Stored Invalid Serial Data Received

DTC C0561 F1
- System Disabled Information Stored Invalid Serial Data Received

DTC C0561 71
- System Disabled Information Stored Invalid Serial Data Received

Circuit/System Description

Diagnostics are used to determine whether or not there is a fault with the brake pressure, wheel speed or autonomous trailer braking request data being received by the trailer brake control module (TBCM) over GMLAN serial data.

The loss of serial data brake pressure diagnostic is to determine whether or not there is a fault with the brake pressure data being received over GMLAN. This diagnostic looks at the brake pressure signal validity and protection value signals over a period of time to determine the fault state of the brake pressure sensor.

The loss of serial data wheel speed diagnostic is to determine whether or not there is a fault with the wheel speed data being received over GMLAN. This diagnostic looks at the wheel speed signal validity and sequence number errors over a period of time to determine the fault state.

The loss of serial data autonomous trailer braking request diagnostic is to determine whether or not there is a fault with the autonomous trailer braking request data being received over GMLAN. This diagnostic looks at the autonomous trailer braking request protection value signals and sequence number errors over a period of time to determine the fault state.

Conditions for Running the DTC

* Ignition ON.
* Ignition voltage is 9.5-17 V.

Conditions for Setting the DTC

* The EBCM diagnoses a fault condition in the master cylinder pressure sensor, and sends a serial data message to the trailer brake control module.
* The EBCM diagnoses a fault condition in the wheel speed sensors, and sends a serial data message to the trailer brake control module.
* The TBCM diagnoses a fault condition in the autonomous trailer braking request serial data message.

Action Taken When the DTC Sets

DTC C0561 F0 or DTC C0561 F1
* The trailer brake control will be disabled for the remainder of the ignition cycle.
* The driver information center will display Service Trailer Brake System.

DTC C0561 71

The trailer brake control will not be disabled for the remainder of the ignition cycle.

Conditions for Clearing the DTC

* The condition for the DTC is no longer present.
* The TBCM clears the history DTC when a current DTC is not detected in 40 consecutive drive cycles.

Reference Information
Schematic Reference

Trailer Brake Control Schematics [1][2]Electrical Diagrams
Connector End View Reference

Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)
Description and Operation

Trailer Brake Controls Description and Operation Description and Operation
Electrical Information Reference

* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

1. Verify that DTC U0100, U0121, U0140 or U2099 are not set.

• If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.

2. Verify that DTC C0035, C0040, C0045, C0050, or C0131 are not set.

• If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.

3. Verify that DTC U0438 or C0561 71 are not set.

• If DTC U0438 is set, reprogram the EBCM.
• If DTC C0561 71 is set, reprogram the trailer brake control module (TBCM).

4. Replace the trailer brake control module (TBCM).

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

* Trailer Brake Control Module Replacement
* Control Module References Control Module References for EBCM or TBCM replacement, programming and setup