Restore Safe Towing and Clear That Annoying Dash Light for Good
If you own a GM HD truck, you know how crucial it is to have a fully functional towing system. The “Service Trailer Brake System” message on your dash isn’t just an annoyance—it’s a critical safety warning. It means your truck’s ability to control your trailer’s brakes is compromised. As a technician with over two decades of experience, I’ve seen firsthand how a faulty Trailer Brake Control Module (TBCM) can turn a routine haul into a dangerous situation. This module is the brain of your trailer braking system, and when it fails, you lose that essential control.
We offer a reliable, straightforward solution: a genuine GM Trailer Brake Control Module (part number 20850923), professionally programmed to your truck’s specific Vehicle Identification Number (VIN) before it ever leaves our facility. This means you get a part that is truly plug-and-play, eliminating the need for an expensive trip to the dealership for programming. Simply install it, and you’re ready to tow with confidence again.
From the Diagnostic Bay
I remember a customer, a contractor, who brought in his 2014 Sierra 2500. His complaint was an intermittent “Service Trailer Brake System” light and the trailer brakes grabbing unpredictably. He’d already replaced the trailer-side wiring. Upon inspection, we found the TBCM, mounted on the driver-side frame rail, had significant corrosion on the connector pins. Its location makes it vulnerable to road salt and moisture. We swapped in a VIN-programmed module, and the problem was solved instantly. This is a classic failure point, and our pre-programmed 2013-2014 Silverado 3500 TBCM is the most efficient fix I’ve found, saving my customers both time and money.
Common Signs of a Failing TBCM
Not sure if your TBCM is the culprit? If your truck is showing any of these symptoms, a failing module is the most likely cause. This is especially true if you see diagnostic trouble codes (DTCs) like C0299 or U-series communication codes related to the trailer brake system.
- ✔ “Service Trailer Brake System” message appears on the Driver Information Center (DIC).
- ✔ No power output to the trailer brakes when the manual slide or brake pedal is applied.
- ✔ Trailer brakes are either not working at all or are engaging erratically.
- ✔ The integrated trailer brake controller gain adjustment doesn’t respond.
- ✔ Intermittent “Trailer Connected” / “Trailer Disconnected” messages without a trailer attached.
A Straightforward Guide to Installation
Replacing the 2013-2014 Silverado 3500 TBCM is a job most DIYers can handle with basic tools. Because we program it for you, there are no complex electronic steps required post-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 frame on the driver’s side, typically near the rear axle. For Suburbans and Yukons, it’s often on the driver’s side middle of the frame.
- Disconnect and Remove: Carefully unplug the electrical connectors. Press the release tabs firmly. Then, unbolt the module from the frame. These bolts can be rusty, so a little penetrating oil might help.
- Install the New Module: Bolt the new, pre-programmed TBCM into the same location. Ensure it is securely fastened.
- Reconnect and Test: Plug the electrical connectors into the new module until they click into place. Reconnect the battery terminal. Start the truck—the “Service Trailer Brake System” message should be gone. Hook up a trailer to verify correct brake operation before hitting the road.
Verified Vehicle Compatibility
This module is a direct-fit replacement for the following vehicles equipped with the integrated trailer brake control system. It is a compatible replacement for part numbers 20964299 and 20850923.
- ✔ 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
Don’t let a faulty module sideline your work or your weekend plans. This pre-programmed 2013-2014 Silverado 3500 TBCM is the definitive solution to get you back on the road safely and quickly.
Frequently Asked Questions
Do I need to take this part to a dealer for programming?
No. We program the module to your vehicle’s VIN before we ship it. This makes the installation a simple plug-and-play process, saving you hundreds in dealership fees and time.
Where is the TBCM located on my 2014 Silverado 3500?
You will find the Trailer Brake Control Module mounted on the frame rail on the driver’s side (LH), typically toward the rear of the truck near the spare tire.
Will this fix the ‘Service Trailer Brake System’ message?
Yes, in the vast majority of cases, a failing TBCM is the direct cause of this warning message. Replacing it with our pre-programmed unit is the most common and effective repair.
What information do you need from me?
After you place your order, we will need you to provide your 17-digit Vehicle Identification Number (VIN). This ensures we can load the correct GM software and calibrations for your specific truck.
Is this a genuine GM part?
Yes, this is a genuine GM part (or an OEM-equivalent that meets or exceeds GM specifications) that we program with official GM software. This ensures perfect compatibility and long-term reliability.