Restore Your Truck’s Towing Power and Safety
Seeing the dreaded “Service Trailer Brake System” message on your dash? It’s a common and frustrating issue for hardworking GM truck owners. In my 20+ years in the shop, I’ve seen firsthand how a faulty Trailer Brake Control Module (TBCM) can bring your towing operations to a complete halt. Located on the left-hand frame rail, the original module is constantly exposed to road salt, water, and debris, leading to corrosion and internal failure. This isn’t just an annoyance; it’s a critical safety issue that compromises your ability to control a heavy trailer.
This is your direct-fit, reliable solution. We offer a genuine GM Trailer Brake Control Module, part number 20964299, that solves these common problems. The best part? We handle the complex part for you. Before this module ships, our technicians will program it specifically to your truck’s Vehicle Identification Number (VIN). This means it arrives at your door ready for a true plug-and-play installation, saving you from a costly and time-consuming trip to the dealership for programming. Get your 2013-2014 Sierra 3500 TBCM back in perfect working order and tow with confidence again.
From the Diagnostic Bay
I remember a contractor, Mark, who brought his 2014 Silverado 2500 into my shop. He was losing money every day his truck was down. His dash was lit up with trailer brake warnings, and his electric-over-hydraulic brakes on his new equipment trailer wouldn’t work at all. He was worried about a complex wiring nightmare. After a quick scan, I saw communication loss codes pointing to the TBCM. A visual inspection confirmed it—the module was heavily corroded. The dealer quoted him over $600 for the part and programming, plus a two-day wait. Instead, we got him this pre-programmed module. He installed it himself in under 30 minutes in the shop parking lot. The codes cleared, the message was gone, and he was back on the job site the same afternoon. That’s the value of a ready-to-install part.
Is Your Truck Showing These Symptoms?
A failing TBCM will give you clear warning signs. If you’re experiencing any of the following, this module is the likely solution. Over the years, I’ve found these are the most common indicators, often accompanied by diagnostic trouble codes (DTCs) like U0100, U0140, or C0299.
- âś” “Service Trailer Brake System” message appears on the Driver Information Center (DIC).
- âś” Trailer brakes do not engage or work intermittently when the pedal is pressed or manual slider is used.
- âś” The trailer gain display on the dash shows dashes or is inoperative.
- âś” “Trailer Connected” and “Trailer Disconnected” messages flicker on and off.
- âś” No output voltage to the 7-pin trailer connector’s brake pin.
- âś” Audible clicking or buzzing from the module area.
A Straightforward Guide to Installation
You don’t need to be a master mechanic to replace this module. With basic hand tools, you can get this job done in your own driveway. The key is our pre-programming service, which eliminates the need for any special scan tools.
- Safety First: Disconnect the negative terminal from your truck’s battery to prevent any electrical shorts.
- Locate the Module: Find the old TBCM. On most Sierra and Silverado pickups, it’s mounted to the inside of the frame rail on the driver’s side, just in front of the rear axle. On Suburbans and Yukons, it’s typically on the driver’s side frame rail, near the middle of the vehicle.
- Disconnect and Remove: Unplug the two electrical connectors. They have locking tabs, so be gentle. Then, remove the bolts or nuts (usually 10mm or 13mm) holding the module to the frame.
- Install the New Module: Mount your new, pre-programmed TBCM onto the frame using the original hardware. Ensure it is secure.
- Connect and Test: Plug the two electrical connectors firmly into the new module until they click. Reconnect your battery terminal. Start the truck—the “Service Trailer Brake System” message should be gone. Hook up your trailer to verify full functionality.
Guaranteed Fitment for Your GM HD Truck
This module is a direct replacement for part numbers 20964299 and 20850923. It is guaranteed to fit and function correctly on the following vehicles equipped with the factory towing package:
- âś” 2013-2014 Chevrolet Silverado 2500 HD / 3500 HD
- âś” 2013-2014 GMC Sierra 2500 HD / 3500 HD
- âś” 2013-2014 GMC Sierra Denali 2500 HD / 3500 HD
- âś” 2013 Chevrolet Suburban 2500
- âś” 2013 GMC Yukon XL 2500
This is the definitive solution for restoring the integrated trailer brake system on your 2013-2014 Sierra 3500 TBCM and related GM models, ensuring a safe and reliable towing experience every time you hit the road.
Frequently Asked Questions
Why do I need to provide my VIN?
Your VIN is essential for us to program the module with the correct software and calibrations for your truck’s specific options. This ensures it communicates perfectly with your vehicle’s other computers, making the installation truly plug-and-play.
Will this 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 fault, this part will resolve the warning light and restore function.
Is this part difficult to install myself?
Not at all. The physical replacement is very straightforward, typically requiring only basic hand tools to unbolt the old module and mount the new one. Since we pre-program it, you avoid the most difficult part—the dealer-level computer programming.
How do I find the TBCM on my truck?
On most 2013-2014 Silverado and Sierra HD pickups, look on the inside of the driver-side frame rail, usually just ahead of the rear axle. It’s a small black box with two wiring harnesses connected to it.
Is this compatible with part number 20850923?
Yes, this module, 20964299, is the updated and fully compatible replacement for the older part number 20850923. It will function identically once programmed for your vehicle.