C1118

DTC C1118

Diagnostic Instructions

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

DTC Descriptor
DTC C1118
- Trailer Brake Control Sensitivity Switch Circuit

DTC C1118 08
- Trailer Brake Control Sensitivity Switch Circuit Signal Invalid

Diagnostic Fault Information





Circuit/System Description

The User Gain Switch consists of 2 control buttons-Gain Up, and Gain Down. The output signal from the trailer brake controller switch is connected, and monitored by trailer brake control module (TBCM).

The TBCM monitors the circuit fault for User Gain Switch input for faults that includes short to GND, short to battery, and open circuit. This DTC will also be reported when fault is detected in TBCM ground circuit.

The TBCM also monitors the input signal validity from the User Gain Switch.

Conditions for Running the DTC

* The system voltage is in the range of 9.5-17 volts.
* The module is powered up and completes initialization.

Conditions for Setting the DTC

C1118

This DTC will set as current DTC, if one of the following conditions is true for more than 1 second:

* The TBCM detects an open in the user gain switch circuit.
* The TBCM detects short to ground in the user gain switch circuit.
* The TBCM detects short to battery positive in the user gain switch circuit.

C1118 08

This DTC will set as current, if one of the following cases is true:

* The TBCM detects the user gain switch is stuck before the ignition is on, and continuously stuck after ignition was turn on for 30 seconds.
* The TBCM detects the user gain switch is stuck continuously after ignition was turn on for 5 minutes.

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.

When the TBCM ground is open circuit, in addition to setting DTC C1118, DTC C1116 and C1117 may also be cause these DTC to set. In this case, diagnose the TBCM ground first for open circuit fault before to diagnosing DTC C1118.

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 trailer brake controls user gain parameter. The reading should be between 0-100 percent, and change with operating the gain switch up or gain switch down.
2. The reading should be between 0-100 percent, and change with operating the gain switch up or gain switch down.

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 trailer brake controller switch module.
2. Test for less than 5 ohms of resistance between the ground circuit terminal 8 and ground.

* If greater than the specified range, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the TBCM.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 6 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. If all circuits test normal, test or replace the trailer brake controller switch module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

Refer to to Programming and Relearning for programming and setup procedures. Programming and Relearning

* Trailer Brake Control Module Replacement