Brake Controller Install Mercedes SUV

Many Mercedes Benz SUVs come pre-wired for easy brake controller installation

Large trailers, like travel trailers, typically require a trailer brake system. A trailer brake controller is required to operate most trailer braking systems. Some vehicles come equipped with brake controllers and some do not.

Our 2012 Mercedes Benz with the factory towing package does not have a factory trailer brake controller, but is pre-wired for easy installation of a aftermarket brake controller, like the Tekonsha P3 90195 that we planned to use. Here is a quick review of the install.

Install a brake controller in a mercedes suv.
Tekonsha P3 brake controller install in a Mercedes Benz SUV

Before you start, make sure you have the correct wire harness adapter for your vehicle. Many of the mid 2010’s use the Tekonsha 3066-P adapter for the Tekonsha P3 (highly recommended) brake controller. Most of the Mercedes Benz SUVs with the factory towing package have a prewire harness tucked under the driver side dash which will connect to the adapter which connects to the controller.

Overview | Install a trailer brake controller in a GL450

Project Goal: To install an electronic trailer brake controller in a Mercedes SUV using the existing prewire harness.
Difficulty: Beginner
Time: 2 Hours
Install a trailer brake controller in a GL450 Cost: $200

Supplies List | Install a trailer brake controller in a GL450

Tools List | Install a trailer brake controller in a GL450

Steps | Install a trailer brake controller in a GL450

  1. Remove driver's side dash kick panel to locate brake controller prewire
  2. Use a Torx T20 bit (or the proper bit for your specific panels screws), loosen the mounting screws for the driver-side below dash kick panel located just under the steering wheel assembly. Once loosened, gently open the panel to expose the wiring behind the panel.

  3. Connect wiring adapter and plan wire path to brake controller mount location
  4. Connect the wiring adapter and trail the wire path to the planned brake controller mount location. I passed the wiring adapter out the side of the panel and planned to mount the brake controller using the outer-most panel screw.

  5. Mount the trailer brake controller and close the kick panel
  6. Attach the wiring adapter to the brake controller to test for operation. Ensure the wiring connector is securely fastened to the controller. Next, mount the brake controller. If using a proportional brake controller, consider a mounting location that will allow a level, flat orientation of the unit. Proportional brake controllers use sensors and accelerometers to calculate braking current. Non-level or tilted mounting of the controller can affect performance. Next close the kick panel by replacing the removed panel screws. Make sure you've passed the brake controller wiring prior to closing the panel.

    Finally, mount the controller. I used the outermost kick panel mounting screw to mount the brake controller bracket (Tekonsha 5906) and controller.

  7. Connect the brake controller and test the unit
  8. Test the unit with the trailer connected. With this Tekonsha P3 brake controller, the trailer will need to be connected to the trailer to set up and test the unit. If no trailer is connected the unit will display "No Trailer". Once the trailer is connected, walk through the setup menu to configure the unit to your specific trailer. Test the function of the trailer brakes in a safe area prior to using the unit in traffic and at speed.


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