How to Troubleshoot a Brake Controller That Keeps Losing Its Trailer Connection

Updated 10/23/2026 | Published 10/14/2026

Products Featured in This Question

Universal Installation Kit for Trailer Brake Controller - 7-Way RV and 4-Way Flat - 10 Gauge Wires

(3569)

$118.45

Curt 7-Way to RV Socket LED Circuit Tester - Vehicle End

(219)

$22.69

Question:

5 years ago I bought your 31345 and ETBC7 products, they have worked reliably for 5 years. Now my brake controller cannot detect when my trailer is connected, or it loses connection immediately after I connect. Do you have a trouble shooting or diagnosis guide?

asked by: David M

Expert Reply:

Hello David,

Thanks for writing in, and I'm glad to hear everything has worked well for the past five years.

Since your brake controller is either not recognizing the trailer or losing the connection right away, I would start by checking the 7-way connectors on both your vehicle and trailer. Look for any corrosion, moisture, loose terminals, or damaged wiring. After five years of use, these are good places to start.

Next, I would check the ground connections on both the vehicle and trailer, making sure they are secure and attached to clean, bare metal.

You will want to use something like the Curt 7-Way to RV Socket LED Circuit Tester # C73NR. This plugs directly into your vehicle's 7-way connector and has LED lights that show which circuits are working. You can use it to check the vehicle's wiring, although some brake controllers may not recognize the tester as a connected trailer.

I attached a help article as well that walks you through troubleshooting brake controllers.

What brake controller are you using, and what vehicle are you towing with? Also, is the controller displaying any error messages when it loses the trailer connection?

expert reply by: Kate F

David M.

10/14/2026

I have a 2019 Chevy Express Van 3500 extended, I am using a prodigy p2 controller. I have a 7 pin tester, and it shows as working: 12v connection, left and right signal, hazards, brake lights, and tail/ marker lights. When I press the brake pedal, the 7 pin tester lights up the brake lights but the electric brake light flutters, the controller also sees the trailer briefly sometimes when I plug it in, but then goes to "no connection" very quickly.

Kate F.

10/14/2026

@DavidM Thanks for getting back to me with that information. Since the other functions on your 7-way are testing correctly, I would focus on the brake output circuit. One thing to keep in mind is that your Prodigy P2 is a proportional brake controller, so when you're sitting still and pressing the brake pedal, you won't necessarily get a steady brake output signal. That could explain why the electric brake light on your tester is flickering. I would start by using the manual override on your P2 while watching the electric brake light on your 7-way tester. This will let you check the brake output without relying on the brake pedal. Just keep in mind that some testers don't provide enough of a load for the controller to recognize a trailer. Since your controller is briefly recognizing the trailer and then losing the connection, I would also check the blue brake output wire running from the controller to the 7-way, along with the trailer's brake wiring and ground connections. A loose connection or corrosion could be causing the intermittent connection. When you use the manual override on your P2, does the electric brake light on your tester stay on, or does it flicker and go out like it does when you press the brake pedal?

David

10/21/2026

@KateF I learned 7 pin testers don't necessarily have the resistance for brake controllers to recognize something is connected to the 7 pin connector. I took a 12 volt testing lamp and used it for each pin, and everything worked fine. Leading me to be confused, everything on the trailer works because I tested it with another vehicle, and everything on the van works. I plugged in the trailer again and found out that if the plug was halfway on, everything worked, but fully plugged in the trailer brakes stopped working. It was the trailer brake pin on the van. I worked on spreading that pin out a bit, as well as cleaning it with electrical cleaner and a small brass brush (next time I will unplug the battery before doing that ?). Now it works fine. Hard to diagnose pins that are a little imperfect!

Kate F.

10/23/2026

@David I'm glad you got it figured out, and thanks for coming back to share what you found. Those pesky pins can definitely make troubleshooting frustrating, especially when everything tests correctly until the trailer is fully plugged in. That's a great reminder that even a slightly loose terminal can cause an intermittent connection. And yes, disconnecting the power before cleaning those terminals is always a good idea. Glad you're back up and running.