Trailer Brake Controls

DTC C0561 (Gasoline Without LY6)

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

Circuit/System Description

Diagnostics are used to determine whether or not there is a fault with the brake pressure or wheel speed data being received by the fuel pump/trailer brake control module 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

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 fuel pump/trailer brake control module.
* The EBCM diagnoses a fault condition in the wheel speed sensors, and sends a serial data message to the fuel pump/trailer brake control module.

Action Taken When the DTC Sets

* The trailer brake control will be disabled for the remainder of the ignition cycle.
* The driver information center (DIC) will display Service Trailer Brake System.

Conditions for Clearing the DTC

* The condition for the DTC is no longer present.
* The fuel pump/trailer brake control module 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. Replace the fuel pump/trailer brake control module.

Repair Instructions

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

Control Module References Control Module References for fuel pump/trailer brake control module replacement, programming and setup