Seeing the dreaded “Service Trailer Brake System” message on your 2013-2014 Sierra Denali 2500 or Silverado HD? You’re not alone. As a technician with over two decades of experience, I’ve seen this exact issue hundreds of times. The trailer brake control module (TBCM), mounted on the driver-side frame rail, is constantly exposed to road salt, water, and debris, leading to corrosion and internal failure. This isn’t just an annoying light on your dash; it’s a critical safety failure that leaves you without proper braking control for your trailer.
This is your direct-fit, hassle-free solution. We are offering a genuine GM Trailer Brake Control Module, part number 20964299 (also compatible with 20850923), that solves this common problem for good. The best part? We handle the most complicated step for you. Before this module ever leaves our facility, we will program it specifically to your truck’s Vehicle Identification Number (VIN) with the latest, most stable software from General Motors. This means you can skip the expensive trip to the dealership for programming. It arrives at your door ready for a simple, plug-and-play installation.
Common Signs of a Failing TBCM
- ✔ The “Service Trailer Brake System” message is constantly on or appears intermittently.
- ✔ No output or erratic output from the trailer brake controller slider/switch.
- ✔ The truck’s information center shows “Trailer Connected” and “Trailer Disconnected” randomly.
- ✔ Complete loss of communication with the module, often triggering diagnostic trouble codes (DTCs) like U0100 or other U-series codes.
- ✔ Inability to adjust trailer brake gain.
From the Diagnostic Bay
I remember a customer with a 2014 Silverado 2500 who was about to leave on a cross-country trip with his fifth-wheel. The morning he was set to depart, the “Service Trailer Brake” light came on. He was in a panic, thinking his vacation was ruined. We got his truck on the lift and immediately saw the issue. The original TBCM was caked in mud and corrosion. The connectors were green with decay. After confirming power and ground were good, we knew the module was shot. We installed one of our VIN-programmed modules, and within 30 minutes, the light was off, the system was fully functional, and he was safely on his way. That’s the peace of mind this part provides.
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 Sierra and Silverado pickups, the TBCM is mounted to the inside of the frame rail on the driver’s side, roughly above the rear axle. For Suburbans and Yukons, it’s typically on the LH middle of the frame.
- ✔ 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 old module to the frame.
- ✔ Install the New Module: Bolt the new, pre-programmed module into place. Be sure to clean the connectors with electrical contact cleaner before plugging them into the new TBCM for a solid connection.
- ✔ Final Steps: Reconnect the negative battery terminal. Start the truck and test the system. The warning message should be gone, and you can now tow with restored safety and control.
Will This Fit My Truck or SUV?
This module is a guaranteed fit for the following vehicles equipped with the factory towing package. Please verify your vehicle is on this list before ordering.
- ✔ 2013-2014 Sierra 2500 Pickup (Towing Control; LH rear frame)
- ✔ 2013-2014 Sierra 3500 Pickup (Towing Control; LH rear frame)
- ✔ 2013-2014 Sierra Denali 2500 (Towing Control; LH rear frame)
- ✔ 2013-2014 Sierra Denali 3500 (Towing Control; LH rear frame)
- ✔ 2013-2014 Silverado 2500 Pickup (Towing Control; LH rear frame)
- ✔ 2013-2014 Silverado 3500 Pickup (Towing Control; LH rear frame)
- ✔ 2013 Suburban 2500 (Towing Control; LH middle of frame)
- ✔ 2013 Yukon XL 2500 (Towing Control; LH middle of frame)
By purchasing this 2013-2014 Sierra Trailer Brake Module, you’re not just buying a part; you’re buying a complete, ready-to-install repair that restores the integrity and safety of your truck’s towing system. Don’t let a faulty module sideline you—get the reliable fix you need.
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. It arrives ready to be installed, saving you time and money.
What information do you need from me?
After you complete your purchase, please provide us with your 17-digit Vehicle Identification Number (VIN). We cannot ship the part without it.
Is this a difficult part to install myself?
For most individuals with basic mechanical skills, this is a very straightforward installation. It involves unbolting the old module and bolting the new one in its place. No special tools are required.
Where is the TBCM located on my 2014 Sierra 2500?
It is mounted on the inside of the driver-side frame rail, typically near the spare tire or above the rear axle.
Is this a genuine GM part?
Yes, this is a genuine GM component loaded with the latest official GM software for your specific vehicle.
Will this fix the “Service Trailer Brake System” warning?
In the vast majority of cases, a failed TBCM is the cause of this warning message. Replacing it with our pre-programmed module is the correct and reliable repair.