Restore Safe Towing with a Reliable, Pre-Programmed TBCM
If you’re seeing the dreaded “Service Trailer Brake System” message on your dash, you’re not alone. It’s a common and frustrating issue for hardworking GM truck owners. This warning often points directly to a failing Trailer Brake Control Module (TBCM), a critical component for safe towing. Driving with a faulty TBCM compromises your ability to control your trailer’s brakes, creating a significant safety hazard for you and others on the road. Don’t let a small electronic module sideline your truck or put your payload at risk.
We offer a dependable and straightforward solution: a genuine GM Trailer Brake Control Module, part number 20850923 (also compatible with 20964299). The best part? We flash it with the latest GM software and program it specifically to your truck’s Vehicle Identification Number (VIN) before it ships. This means you get a true plug-and-play part that’s ready for installation right out of the box, saving you from a costly and time-consuming trip to the dealership for programming. This is the definitive fix for your 2013-2014 Sierra 3500 TBCM issues.
From the Diagnostic Bay
I’ve seen hundreds of these GM HD trucks in my shop over the years, and a faulty TBCM is one of the most frequent complaints for towers. A recent customer with a 2014 Silverado 2500 had an intermittent “Trailer Disconnected” warning, even when his trailer was securely hitched. His trailer brakes were grabbing unpredictably. The culprit was the original TBCM. Because it’s mounted on the frame rail, it’s exposed to years of road salt, water, and grime. Corrosion had worked its way into the housing, shorting the internal circuits. We swapped it with one of these pre-programmed units in under 30 minutes. The customer was back on the road, towing safely, without the dealership hassle.
Is Your Truck Showing These Symptoms?
A failing TBCM will give you clear warning signs. If you’re experiencing any of the following, it’s time for a replacement:
- ✔ “Service Trailer Brake System” message illuminated on the Driver Information Center (DIC).
- ✔ Trailer brakes not engaging or engaging erratically when you apply the vehicle’s brakes.
- ✔ The manual trailer brake slide controller is unresponsive.
- ✔ Constant “Trailer Connected” / “Trailer Disconnected” messages, even with no trailer attached.
- ✔ Diagnostic Trouble Codes (DTCs) stored in the system, such as U0100 (Lost Communication With ECM/PCM) or C-series codes related to brake circuits.
A Straightforward Guide to Installation
Replacing your 2013-2014 Sierra 3500 TBCM is a job most DIYers can handle with basic tools. Since this module comes pre-programmed, no special scan tools are needed.
- 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. On Suburbans and Yukons, it’s often on the driver’s side frame, closer to the middle of the vehicle.
- Disconnect and Remove: Carefully unplug the two electrical connectors. They have locking tabs that need to be depressed. Then, remove the bolts or nuts holding the module to its bracket on the frame.
- Install the New Module: Bolt the new, pre-programmed TBCM into place. Reconnect the two electrical connectors, ensuring they click securely into place.
- Final Steps: Reconnect the negative battery terminal. Start the truck and verify that the “Service Trailer Brake System” message is gone. Test functionality with a trailer if possible.
Guaranteed Fitment for Your GM HD Truck or SUV
This module is a direct-fit replacement for a range of GM vehicles. Please confirm your model and year from the list below. Upon purchase, you must provide your VIN so we can ensure perfect programming for your specific vehicle options.
- 2013-2014 GMC Sierra 2500/3500 Pickup (Towing Control; LH rear frame)
- 2013-2014 GMC Sierra Denali 2500/3500 (Towing Control; LH rear frame)
- 2013-2014 Chevrolet Silverado 2500/3500 Pickup (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)
Frequently Asked Questions About the 2013-2014 Sierra 3500 TBCM
Frequently Asked Questions
Why do you need my VIN?
Your truck’s VIN allows us to program the module with the exact software and calibrations from GM for your vehicle’s specific features. This ensures it works perfectly upon installation without needing a dealer visit.
Will this part fix the “Service Trailer Brake System” light?
In the vast majority of cases, yes. This warning is the most common symptom of a failed TBCM. As long as the module is the source of the fault, this part will resolve the issue.
Is this a difficult part to install myself?
Not at all. For most people with basic mechanical skills, this is a 30-minute job. It involves locating the module on the frame, unplugging two connectors, and removing a few bolts. Since it’s pre-programmed, the electronic side is simply plug-and-play.
What happens if I keep driving with a bad TBCM?
Continuing to drive with a faulty TBCM is a safety risk. You will not have proper control over your trailer’s brakes, which can dramatically increase stopping distances and lead to trailer sway, especially when carrying a heavy load.
Are part numbers 20850923 and 20964299 the same?
Yes, they are compatible and interchangeable part numbers from GM. This module serves as a direct replacement for either number.