Restore Safe Towing and Clear That Annoying Dash Light
Seeing the ‘Service Trailer Brake System’ message on your 2013-2014 Silverado or Sierra HD is more than just an annoyance—it’s a critical safety warning. When you’re hauling heavy equipment, a boat, or a camper, you depend on your trailer brakes to work flawlessly with your truck. The Trailer Brake Control Module (TBCM) is the brain behind that operation, and when it fails, you lose that essential control and confidence. In my 20+ years as a technician, I’ve seen countless trucks come into the shop with this exact issue, often leaving the owner unable to tow safely or pass a vehicle inspection.
This isn’t a part you can afford to ignore. A faulty TBCM can lead to dangerous situations on the road, with trailer brakes that don’t engage, engage erratically, or lock up unexpectedly. This replacement TBCM, part number 20850923, is the definitive solution. The best part? We handle the programming for you. Simply provide your VIN at checkout, and we’ll flash the module with the latest official GM software specifically for your truck. It arrives at your door ready to install, saving you a costly trip to the dealership and their programming fees. This is the most direct and reliable way to get your 2013-2014 Silverado 3500 TBCM system back to factory-perfect operation.
A Technician’s Notebook
A customer brought in his 2014 Sierra 2500 last month, frustrated with an intermittent ‘Service Trailer Brake’ light and a ‘Check Trailer Wiring’ message that would pop up randomly, even with a known-good trailer. He’d already replaced the 7-pin connector at the bumper to no avail. When we put it on the lift, the cause was immediately clear. The TBCM, mounted on the left-hand frame rail, was caked in mud and its connectors were showing signs of green corrosion. These modules live in a harsh environment, constantly exposed to water, salt, and road debris. Over time, moisture gets past the seals and compromises the internal circuit board. We installed one of our VIN-programmed modules, and the problem was solved instantly. This is a classic failure I’ve diagnosed hundreds of times, and a direct replacement is the only long-term fix.
Common Signs of a Failing TBCM
- ✔ ‘Service Trailer Brake System’ message is constantly on your driver information center.
- ✔ The trailer gain adjustment on your dash is unresponsive or shows ‘—‘.
- ✔ Your trailer brakes feel weak, grabby, or don’t work at all when connected.
- ✔ Diagnostic trouble codes (DTCs) related to the trailer brake control circuit are stored in the system.
- ✔ You experience a ‘Check Trailer Wiring’ message even when the trailer wiring is perfectly fine.
Plug-and-Play Installation: Get Back on the Road Fast
Replacing your 2013-2014 Silverado 3500 TBCM is a straightforward job that most DIYers can handle in their own driveway. Since we program it beforehand, you won’t need any special scan tools.
- Safety First: Disconnect the negative terminal from your truck’s battery to prevent any electrical shorts.
- Locate the Module: On pickup models, the TBCM is mounted to the inside of the frame rail on the driver’s side (LH), typically just ahead of the rear axle. On Suburban/Yukon XL models, it’s on the LH side, near the middle of the frame.
- Disconnect and Remove: Carefully unplug the electrical connectors. Press the release tabs firmly and pull straight out. Avoid wiggling them excessively. Then, remove the bolts or nuts holding the module bracket to the frame.
- Install the New Module: Bolt the new, pre-programmed TBCM into the original location. Ensure it is securely fastened to the frame.
- Reconnect and Test: Plug the electrical connectors into the new module until they click into place, ensuring a secure connection. Reconnect your battery terminal. Start the truck; the ‘Service Trailer Brake’ message should now be gone. Hook up a trailer to fully test the braking function.
Verified Vehicle Compatibility
This module is a guaranteed direct-fit replacement for the following vehicles, restoring full towing control. It is a compatible replacement for part numbers 20850923 and 20964299.
- 2013-2014 Chevrolet Silverado 2500/3500 Pickup (Towing Control; LH rear frame)
- 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 Chevrolet Suburban 2500 (Towing Control; LH middle of frame)
- 2013 GMC Yukon XL 2500 (Towing Control; LH middle of frame)
Don’t let a faulty module compromise your safety. Order today, provide your VIN, and get the right part, programmed and ready to install, delivered right to your door. Restore your truck’s full capability and tow with confidence again.
Frequently Asked Questions
Do I really need to provide my VIN?
Yes, absolutely. The Vehicle Identification Number (VIN) is essential for us to load the correct GM-certified software and calibrations for your specific truck’s options. This step ensures the 2013-2014 Silverado 3500 TBCM communicates perfectly with your other vehicle systems, making the installation truly plug-and-play.
Is this a difficult part to install myself?
No, for most people with basic hand tools, this is a very manageable job. The module is typically held on by a couple of bolts on the frame rail. The main challenge can be reaching it comfortably. Since we pre-program the unit, you save the most complicated step: a trip to the dealer for software flashing.
Will this fix the ‘Service Trailer Brake System’ message on my dash?
In the vast majority of cases, yes. This message is the most common symptom of a failed TBCM. As long as your vehicle’s wiring and the trailer itself are in good condition, replacing a faulty module with this pre-programmed unit is the definitive fix.
What is the difference between part numbers 20850923 and 20964299?
These are interchangeable GM part numbers. Manufacturers often update part numbers over time due to minor revisions or supplier changes. This module is a direct, compatible replacement for either of those part numbers.
Is this part new or used?
This is a high-quality, inspected, and tested used OEM part, guaranteed for function. We ensure each module is ready for programming and service, providing a reliable and cost-effective alternative to a brand new dealership part.