C1112

DTC C1112

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis
* Diagnostic Procedure Instructions

DTC Descriptor
DTC C1112
- Trailer Brake Control Relay Low Control Circuit - Relay Control Active Low

Diagnostic Fault Information





Circuit/System Description

The trailer brake control module (TBCM) diagnostic monitor detects faults on the solid state relay (SSR) relay control active low circuit.

Conditions for Running the DTC

* The ignition is ON.
* The system voltage is in the range of 9.5 - 17 volts.
* The 5 volt supply for the SSR output auxiliary supply circuit is not faulted, and DTC C0870 is not set as current DTC.
* The SSR relay control circuit fault DTC C1114 is not set as current DTC.
* This DTC runs once per ignition cycle within the enabling conditions.

Conditions for Setting the DTC

DTC C1112 will set as current DTC, if one of the following conditions is true:

* The TBCM detects an open in the relay control active low circuit.
* The TBCM detects short to ground in the relay control active low circuit.
* The TBCM detects short to battery positive in the relay control active low circuit.
* The TBCM detects a open power circuit from fuse 65 or 61.

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 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.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal F and ground.

* If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test or replace the trailer brake controller solid state relay.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal E and ground.

* If less than the specified range, test the 5-volt reference 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 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the TBCM.

4. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal C and ground.

* If less than the specified range, test the 5-volt reference 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 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the TBCM.

5. If all circuits test normal, replace the trailer brake solid state relay.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests

* Trailer Brake Control Module Replacement
* Refer to to Programming and Relearning for programming and setup procedures. Programming and Relearning