Curt Discovery Brake Controller Shows OL Error When Trailer is Connected

Updated 09/19/2025 | Published 06/13/2014

Question:

Hi there I just installed a curt discovery controller in my 2010 silverado....when I touch the brakes with no trailer it shows a decimal on the screen........when I connect the trailer it flashed OL. I am having trouble figuring out where the short is and I have checked all of my wiring connections. I even hooked the trailer up to a friends truck and the brakes on the trailer work fine with his controller......Could it be that I need to install a seperate 20 AMp fuse in the truck ?

asked by: Jentry

Expert Reply:

It is possible that it is a simple wiring issue that is causing the errors on your Curt Discovery brake controller # C84VV. On your 2010 Chevy Silverado, there is a tow package wire bundle under the dash to wire in a brake controller.

The tow package red goes to brake controller black. White goes to white, blue to blue, and the light blue or orange wire on the truck goes to the brake controller red wire.

The OL indicates an overload and if all of the connections at the brake controller are fine AND the trailer works fine on a different truck then there is likely an issue between the brake controller and the trailer connector on the truck.

Make sure that the connector is clean and free of corrosion inside and out. Check the wire from the connector forward on the truck as best as you can and look for exposed wiring touching metal and fix as needed.

It is possible that the truck needs some connections made under the hood but even if the connections were not made the controller should not be reading an overload condition. I have linked a help article that shows the connections you may need to make under the hood along with other installation information.

I have also included some links on articles that explain how to test and troubleshoot brake controllers.

expert reply by: Michael H

Rick

5/8/2020

Need info on connecting Curt discovery break controller in 1995 c2500 suburban wires have been cut in vehicle have wires from controller but not sure what to connect

Chris R.

5/11/2020

I wasn't able to track down the factory wire color/functions for a brake controller on your Chevy Suburban. Your best option here will be to use a circuit tester to actually test them for function - see which one as constant 12V power (black wire on Discovery), which only receives power when the brake pedal is depressed (red wire on Discovery), etc.

Laurel

9/19/2025

Last time I used controller it was fine .went to use it all i get is the decimal (red dot), I couldn't find answers as what to do or what is wrong ..HELP!

Jesse M.

9/19/2025

@Laurel What vehicle is this on? Have you checked your brake controller wiring. This could be due to inadequate power or a bad ground. It could also mean the controller is not detecting a connection with the trailer.