C1113
DTC C1113
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptor
DTC C1113 01
- Trailer Brake Control Relay High Control Circuit Short to Battery
Diagnostic Fault Information
Circuit/System Description
The trailer brake relay control circuit high SSR enable circuit short to battery monitors for short-to-high faults on the trailer brake solid state relay (SSR) enable circuit. In general, the SSR enable short-to-high circuit diagnostic is executed whenever the SSR has been disabled for a minimum duration. Typically, the diagnosis is executed at TBCM power up. The diagnosis test passes, if TBCM detected the status is correct for consecutive 16 samples.
Conditions for Running the DTC
* The ignition is ON.
* This DTC runs once per ignition cycle within the enabling conditions.
Conditions for Setting the DTC
The TBCM detects short to battery positive in the solid state relay control circuit.
Action Taken When the DTC Sets
* The trailer brake control will be disabled for the remainder of the ignition cycle.
* The Service Trailer Brake System will be displayed on the Driver Information Center (DIC).
Condition for Clearing the MIL/DTC
* When the condition for the DTC is no longer present.
* The TBCM automatically clears the history DTC when a current DTC is not detected in 40 consecutive drive cycles.
Diagnostic Aids
If there are any DTCs set for GMLAN communication such as U0100, U0121, U0140, or U2099, diagnose them first before to resolve DTCs described in this section.
If DTC C1114 is set as a current DTC, diagnose first before diagnosing DTC C1113.
If there is an aftermarket trailer brake controller, the ITBC must be disconnected. Do not power both ITBC and aftermarket controllers to control the trailer brakes at the same time.
Circuit/System Verification
1. Ignition ON, observe the scan tool brake controls Trailer Brake Relay Status parameter. The reading should be Enabled or Disabled.
2. Ignition ON, observe the scan tool brake controls TBCM Command Duty Cycle parameter. The reading should be 0-100 percent.
Circuit/System Testing
Important: All electrical components and accessories must be turned OFF and allowed to power down.
1. Ignition OFF, disconnect the harness connector at the solid state relay module.
2. Test for less than 5 ohms of resistance between the ground circuit terminal B and ground.
* If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, test for 9 - 11 volts between the 10-volt relay control circuit terminal E and ground.
* If less than the specified range, test the 10-volt relay control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the TBCM.
* If greater than the specified range, test the 10-volt relay control circuit for a short to voltage. If the circuit tests normal, replace the TBCM.
4. Ignition OFF, reconnect the harness connector at the solid state relay module.
5. Connect a test lamp between the control circuit terminal C of the trailer connector and the ground circuit terminal B.
6. Command the trailer brake relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
* If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the TBCM.
* If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the TBCM.
7. If all circuits test normal, test or replace the trailer brake solid state relay (SSR).
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests
* Trailer Brake Control Module Replacement
* Refer to to Programming and Relearning for programming and setup procedures. Programming and Relearning