Diagnostic Resource Only
Note: Highway 71 Auto Parts provides this guide for diagnostic purposes only. We do not sell or service this specific module. We specialize exclusively in Engine (ECM/PCM), Transmission (TCM), and Body Control Modules (BCM). If your diagnostics point to an Engine or Transmission computer failure, contact us for a programmed replacement.
C0XXX: Decoding Your Trailer Brake Codes
When your bumper-mounted trailer plug isn’t the problem, you need to dive into the diagnostic codes. Here is the technical breakdown of the most common ITBC failures.
Common ITBC Diagnostic Codes
- C1114 / C111B: Trailer Brake Control Output Circuit. This means the module is sending voltage to the trailer, but it’s disappearing. Check for a broken wire near the spare tire.
- C1117: Trailer Brake Control Relay Circuit. The internal relay inside the module is stuck. The module must be replaced.
- C1112: Trailer Brake Control Device. This is an internal self-test failure. The module has “brain damage” and cannot be reset.
👨🔧 Advanced Diagnosis
“You can test the module output with a simple test light. Connect the light to the ‘Brake’ pin and ‘Ground’ pin on your 7-pin plug. Have a helper press the brake. The light should get brighter the harder they press the pedal. If it stays dim or doesn’t light, the TCCM output drive is dead.”