Restore Safe Towing and Clear That Annoying Dash Warning
If you’re staring at the dreaded “Service Trailer Brake System” message on your 2013-2014 Sierra or Silverado HD, you’re not just dealing with an inconvenience—you have a serious safety issue. As a mechanic with over two decades of experience, I’ve seen firsthand how a faulty Trailer Brake Control Module (TBCM) can compromise your ability to stop safely when hauling a heavy load. This isn’t a part you can afford to ignore. That’s why we offer this direct-fit, VIN-programmed TBCM, part number 20850923, to get you back on the road with confidence.
From the Diagnostic Bay: The Telltale Signs of TBCM Failure
A customer brought his 2014 Silverado 2500 into my shop last month, frustrated with an intermittent “Service Trailer Brake” light and no power to his trailer’s brakes. He’d already replaced the 7-pin connector, thinking it was a simple wiring problem. After hooking up my scanner, I saw communication loss codes for the TBCM. A quick look under the truck confirmed my suspicion. The module, mounted on the driver-side frame rail, was caked in road salt and grime. Water intrusion had corroded the connector pins and damaged the internal circuit board—a classic failure I’ve diagnosed hundreds of times on these GM HD trucks. Replacing the module with a pre-programmed unit like this one was the definitive fix.
The Smart Solution: A VIN-Programmed Module Ready for Installation
Why is a VIN-programmed module so important? Your truck’s computer network needs to recognize and communicate with the TBCM correctly. In the past, this meant buying the part and then paying for a costly trip to the dealership for programming. We eliminate that step. Simply provide us with your Vehicle Identification Number (VIN) during checkout, and we will flash this module with the latest, most stable software directly from GM. It arrives at your door ready to be installed, saving you time, hassle, and diagnostic fees.
Is Your Truck Showing These Signs?
- ✔ “Service Trailer Brake System” message constantly on or appearing intermittently.
- ✔ No output or gain adjustment on the integrated trailer brake controller on your dash.
- ✔ Trailer brakes do not engage when you apply the truck’s brakes.
- ✔ The trailer disconnects and reconnects randomly on the driver information center.
- ✔ Diagnostic trouble codes (DTCs) related to the TBCM, such as U0137 (Lost Communication With Trailer Brake Control Module).
A Straightforward Guide to Installation
- Safety First: Disconnect the negative terminal from your truck’s battery to prevent any electrical shorts.
- Locate the Module: On most pickups, the TBCM is mounted to the inside of the driver-side frame rail, roughly above the rear axle. For Suburbans and Yukons, it’s typically on the driver-side frame rail, near the middle of the vehicle.
- Disconnect and Remove: Carefully unplug the electrical connectors. You may need a small flathead screwdriver to release the locking tabs. Then, remove the bolts or nuts holding the module to the frame.
- Install the New Module: Bolt the new, pre-programmed TBCM into the original location. Ensure it is securely fastened.
- Reconnect: Plug the electrical connectors firmly into the new module. You should hear a click as they lock into place.
- Final Step: Reconnect the negative battery terminal. Start the truck and test the system. The “Service Trailer Brake System” message should be gone.
Guaranteed Fitment for Your GM HD Truck or SUV
This module is a direct replacement for part numbers 20850923 and 20964299, ensuring seamless integration with your vehicle’s systems. It is verified to fit the following models:
- 2013-2014 Chevrolet Silverado 2500 & 3500 Pickup
- 2013-2014 GMC Sierra 2500 & 3500 Pickup
- 2013-2014 GMC Sierra Denali 2500 & 3500
- 2013 Chevrolet Suburban 2500
- 2013 GMC Yukon XL 2500
Frequently Asked Questions
What does ‘VIN Programmed’ actually mean?
It means we use your truck’s specific Vehicle Identification Number (VIN) to load the correct GM factory software and calibrations onto the module before we ship it. This ensures it communicates perfectly with your truck’s other computers, just like the original part, without requiring a trip to the dealer.
Will this part fix the ‘Service Trailer Brake System’ message?
In the vast majority of cases, yes. This message is the most common symptom of a failed TBCM. If the module is the source of the problem, this pre-programmed replacement will resolve the error message and restore full function.
Where is this module located on my 2014 Sierra 3500?
On your Sierra 3500 pickup, you will find the TBCM mounted to the inside of the driver-side frame rail, typically located toward the rear of the truck, near the spare tire.
Do I need any special tools for installation?
No special tools are required. Basic hand tools like a socket set and a small screwdriver to help with the connector tabs are all you should need to complete the installation.
Is this part compatible with other part numbers?
Yes, this module, 20850923, is also a direct, compatible replacement for part number 20964299.