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Hooking up trailer lights doesn’t need to be complicated. The Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector plugs directly into your vehicle’s factory wiring behind the tail lights. There’s no wire cutting or splicing required—just plug in the connectors and you’re ready to go.
Heavy trailer loads can overload factory circuits, but this harness includes a powered ModuLite converter that solves that problem. It draws power straight from your vehicle’s battery instead of the tail light wiring, so your electrical system stays isolated and protected. That means steady, reliable lighting for both your vehicle and trailer.
Whether your trailer has LED lights or traditional bulbs, this harness keeps everything working together. The converter ensures the correct signal output for each light type so your running lights, turn signals, and brake lights stay bright and in sync every time you tow.
The harness installs behind the interior trim panels near the tail lights for a clean, factory-style finish. The 4-flat trailer connector routes neatly out of sight when not in use, keeping everything tucked away and protected from dirt and weather.
Once installed, you get a standard 4-flat connector ready for basic trailer lighting—running lights, turn signals, and brake lights. It’s the dependable setup most small trailers use and makes connecting to a trailer quick and straightforward every time.
Customer Satisfaction Score:
93% were satisfied with this product
7% of customers were not satisfied
Ratings & Reviews
Mike
11/12/2023
One year out now and the hitch and the wiring harness are rock solid. I will be buying a couple of mountain bikes pretty soon, sure glad Ive got this hitch. I also used it to haul a rented aerator back and forth from a local rental place. All the trailer lights worked perfectly!
Mike L.
11/17/2023
Jenny N.
10/30/2023
There is a lot going on with this harness. I have a few trouble shooting tips that I would like to have you try. The first would be to check the ground and make sure that it is a good ground that it connected to bare metal on the vehicle. The second would be to take out the fuse in the inline fine connection for 30 second to 1 minute and then re-insert it. If the harness is still experiencing problems then it might need to be replaced.
Helpful Links
Jess
7/23/2025
could not be better. no problems at all. would recommend to anyone.
Brent
7/6/2021
Great product. No issues at all and is still working perfect.
Katrina B.
3/28/2023
Can you please confirm if you are referring to the tapping screw? If so, we can either send you the missing screw or you can take a trip to the hardware store. If not, please let me know what screw you are talking about.
Paul
10/27/2023
The wire harness hasnt failed. Its been perfect since it was installed. The install instructions provided by etrailer were perfect for the install. It made the install much easier.
Mike L.
11/13/2023
Michael
7/20/2021
Still no issues. Wiring harness continues to function properly.
Jenny N.
7/17/2024
Geneva, I can help troubleshoot with the harness. Has the harness just started this or has it always done so? I will first recommend checking the ground connection on the vehicle. Make sure it is a good ground to bare metal. If the ground is good, I would then use a circuit tester like # PTW2993 to test the right and left hand light location on the 4 way. If the signal is not reaching the 4 way then testing the wires before the converter box and after the converter box to see if the signal is making it through. If not then the harness would be considered defective. I also have a FAQ below that will help.
Helpful Links
Geneva
7/18/2024
Still unable to get the blinkers to work with the wiring harness.
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Bla
5/22/2026
I had to cut and reconnect the wires going to the lights since the connectors dont fit through the grommets, and routing them on the outside could interfere with the radar modules behind the rear fascia, but after I completed the installation its been working perfectly. I hope they redesign this by using an actual vehicle.