Regain Control and Tow with Confidence
Seeing the dreaded “SERVICE TRAILER BRAKE SYSTEM” message on your dash is more than an annoyance—it’s a critical safety alert. When you’re hauling a heavy load, you depend on your trailer brakes to work flawlessly. A faulty Trailer Brake Control Module (TBCM) compromises that safety, leaving you with reduced stopping power and a constant, distracting warning. This is a common issue on hardworking GM trucks, but the fix doesn’t have to involve an expensive trip to the dealership.
This is a direct-fit replacement Trailer Brake Control Module for your GM truck. The most significant benefit we offer is our professional, in-house programming service. Before this module ships, we will flash it with the latest official GM software, perfectly matched to your truck’s specific Vehicle Identification Number (VIN). This means when it arrives at your door, it’s ready for a true plug-and-play installation. You get to skip the dealer appointment, avoid their programming fees, and get your truck back to safe towing condition quickly and affordably.
From the Diagnostic Bay
I’ve seen hundreds of these GMT900-platform trucks in my shop with TBCM issues. A classic case was a 2009 Silverado 2500HD used for landscaping. The owner complained of an intermittent “Service Trailer Brake” message and no brake response when he used the manual override switch. A quick scan showed communication loss codes with the TBCM. The module is mounted on the left-hand rear frame rail, a spot notorious for exposure to road salt, water, and debris. Sure enough, we found heavy corrosion on the module’s casing and connectors. After replacing it with a VIN-programmed unit like this one, all codes cleared, and his trailer braking function was fully restored. It’s almost always a hardware failure from its exposed location, not something you can fix without a replacement.
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:
- ✔ “SERVICE TRAILER BRAKE SYSTEM” message on the Driver Information Center (DIC).
- ✔ No output or a blank display when you adjust the trailer gain.
- ✔ The manual trailer brake activation switch does not work.
- ✔ Trailer brakes feel weak or don’t engage at all.
- ✔ Diagnostic Trouble Codes (DTCs) stored in the system, such as C0561, U0100, or other communication-related faults pointing to the TBCM.
A Straightforward Guide to Installation
Because this module comes pre-programmed, the installation is a simple bolt-in process that a confident DIYer can complete in their driveway. No special programming tools are required.
- Safety First: Disconnect the negative terminal from your truck’s battery to prevent any electrical shorts.
- Locate the Module: Find the old TBCM. It’s mounted to the inside of the frame rail on the driver’s side (LH), typically just in front of the rear axle.
- Disconnect: Carefully unplug the electrical connectors from the module. You may need to press a release tab. Inspect the connectors for any corrosion or damage.
- Unbolt the Old Module: Remove the bolts or nuts holding the module to the frame and set the old unit aside.
- Install the New Module: Mount your new, VIN-programmed TBCM in the same location, securing it with the original hardware.
- Reconnect: Firmly plug the electrical connectors into the new module until they click into place.
- Final Step: Reconnect the negative battery terminal. Start the truck and verify that the “Service Trailer Brake System” message is gone.
Will This Fit My Truck?
We guarantee this module is a direct-fit replacement for the following vehicles equipped with the factory towing package. It is a compatible replacement for part numbers 20850923, 25854535, 25788981, and 25907533.
- 2007-2009 Chevrolet Silverado 2500/3500 Pickup (Towing Control; LH rear frame)
- 2007-2009 GMC Sierra 2500/3500 Pickup (Towing Control; LH rear frame)
- 2008-2009 Chevrolet Silverado 1500 Pickup (Towing Control; LH rear frame)
- 2008-2009 GMC Sierra 1500 Pickup (Towing Control; LH rear frame)
- 2008-2009 GMC Sierra Denali (Towing Control; LH rear frame)
Frequently Asked Questions
How do I provide my VIN?
After you complete your purchase, simply send us a message with your 17-digit Vehicle Identification Number (VIN). We cannot program and ship your module without it.
Is this part truly plug-and-play?
Yes. Because we program the module to your specific VIN before shipping, it will communicate correctly with your truck’s other systems right out of the box. No dealer visit is necessary for installation or programming.
What happens if I install it without programming?
An unprogrammed module will not function. It will fail to communicate with your truck’s Body Control Module (BCM) and Engine Control Module (ECM), and you will still have the error message on your dash. Our pre-programming service solves this entire problem for you.
Where is this module located on my 2008 Sierra Denali?
The Trailer Brake Control Module is located on the driver’s side (LH) frame rail, toward the rear of the truck. It’s exposed to the elements, which is a common reason for its failure.