Restore Your Towing Confidence and Clear That Annoying Dash Light
If you own a 2013-2014 GM HD truck, that dreaded “Service Trailer Brake System” message is more than just an annoyance—it’s a critical safety alert. As a mechanic with over two decades of experience, I’ve seen this issue countless times. The Trailer Brake Control Module (TBCM), often mounted on the frame rail, is constantly exposed to road salt, water, and debris. This leads to corrosion and internal failure, compromising your ability to safely control a trailer.
Don’t risk your safety or pay steep dealership prices for a part and programming. We offer a direct, reliable solution. This is a genuine GM-spec Sierra 2500 Trailer Brake Module that arrives at your door fully programmed to your truck’s specific Vehicle Identification Number (VIN). We handle the complex part so you don’t have to. Simply provide your VIN after purchase, and we’ll flash the module with the latest factory software, making installation a true plug-and-play process. Get back to towing with the peace of mind that your equipment is functioning exactly as it should.
From the Diagnostic Bay
A customer brought his 2014 Silverado 3500 dually into my shop last month, frustrated with an intermittent “Service Trailer Brake” light and the trailer gain constantly resetting to zero. He was hauling a heavy fifth-wheel and couldn’t trust his brakes. A quick scan showed communication loss with the TBCM. A visual inspection confirmed my suspicion: the module, located on the driver-side frame rail, was heavily corroded. Instead of a costly dealer visit, we installed one of these VIN-programmed modules. The entire job took less than 30 minutes, the codes cleared instantly, and he was back on the road with fully functional, reliable trailer brakes. This is the exact fix for that common problem.
Is Your Truck Showing These Symptoms?
- ✔ “Service Trailer Brake System” message appears on the Driver Information Center (DIC).
- ✔ Trailer brakes apply erratically or not at all.
- ✔ The manual trailer brake slide controller is unresponsive.
- ✔ Inability to adjust the trailer gain settings.
- ✔ Diagnostic trouble codes (DTCs) related to the TBCM or trailer brake circuit.
- ✔ The truck doesn’t recognize that a trailer is connected.
A Straightforward Guide to Installation
Replacing your Sierra 2500 Trailer Brake Module is a job most DIYers can handle with basic tools. Since we program it beforehand, you can skip the trip to the dealership.
- Safety First: Disconnect the negative terminal from your truck’s battery to prevent any electrical shorts.
- Locate the Module: On most 2500/3500 models, the TBCM is mounted to the driver’s side (LH) frame rail, typically towards the rear, near the spare tire. On Suburban/Yukon XL 2500 models, it’s often on the LH side in the middle of the frame.
- Disconnect Electrical Connectors: Carefully press the release tabs and unplug the wiring harnesses from the old module. Inspect the connectors for any corrosion or damage.
- Unbolt the Old Module: Using a socket wrench, remove the bolts or nuts securing the TBCM to the frame. The old module should now be free.
- Mount the New Module: Position your new, pre-programmed TBCM and secure it with the original mounting hardware.
- Reconnect and Finalize: Plug the wiring harnesses firmly into the new module until they click. Reconnect the negative battery terminal. Start the truck and the “Service Trailer Brake System” message should be gone.
Guaranteed Fitment for Your GM Truck or SUV
This module is a direct replacement for part numbers 20964299 and 20850923. It is guaranteed to fit the following vehicles equipped with the factory towing package:
- 2013-2014 GMC Sierra 2500 HD & 3500 HD (Towing Control; LH rear frame)
- 2013-2014 GMC Sierra Denali 2500 & 3500 (Towing Control; LH rear frame)
- 2013-2014 Chevrolet Silverado 2500 HD & 3500 HD (Towing Control; LH rear frame)
- 2013 Chevrolet Suburban 2500 (Towing Control; LH middle of frame)
- 2013 GMC Yukon XL 2500 (Towing Control; LH middle of frame)
By providing your VIN, you ensure this Sierra 2500 Trailer Brake Module is not only a physical fit but also a perfect electronic match for your vehicle’s systems.
Frequently Asked Questions
Why do I need to provide my VIN for this part?
Your vehicle’s VIN is required so we can program the module with the correct, most current GM software specifically for your truck’s configuration. This ensures seamless communication with other vehicle systems and makes the installation truly plug-and-play, saving you a trip to the dealer.
Where is this TBCM located on my 2014 Sierra 2500?
On the 2013-2014 Sierra and Silverado 2500/3500 models, the module is typically bolted to the inside of the driver’s side (left-hand) frame rail, located between the cab and the rear axle, often near the spare tire.
Will this part definitely fix the ‘Service Trailer Brake System’ message?
In the vast majority of cases, yes. A failed TBCM is the most common cause of this specific warning message on these GM trucks. While other issues like wiring damage are possible, replacing a faulty, corroded module is the standard, reliable repair.
Is this part compatible with part number 20850923?
Yes, this module, part number 20964299, is a fully compatible and updated replacement for the older part number 20850923. It will function identically once programmed to your vehicle.
Do I need any special tools for this installation?
No special tools are required for the installation itself, just basic hand tools like a socket set. Because we pre-program the module, you do not need any expensive diagnostic scan tools for software flashing.