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Wiring a trailer doesn’t have to mean splicing wires or figuring out circuits. The Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector plugs right into the factory wiring at the rear bumper. Once connected, it delivers running light, turn signal, and brake light functions through a standard 4-flat plug. No cutting or soldering—just a clean, plug-and-play install.
If your vehicle didn’t come with a tow package, this kit takes care of that. It includes a relay harness with three relays that install behind the passenger-side kick panel to activate the trailer lighting circuits. The relays supply power to the running lights, turn signals, and brake lamps so your trailer lights work like they should once the harness is plugged in.
The main plug connects at the back of the vehicle using existing factory points, so there’s no need to drill or run wires through tight spots. The 4-flat connector can be mounted to the hitch using a bracket for a tidy finish that keeps the wiring safe and accessible when you’re ready to tow.
Everything about this harness is laid out where you can get to it. The relays sit behind the passenger-side kick panel, and the 4-pole connector routes cleanly to the driver-side frame rail near the bumper. If you ever need to check fuses or relays, their locations are straightforward and easy to reach.
Once installed, you get a reliable 4-way flat connector that powers your trailer’s running lights, brake lights, and turn signals. It’s the standard connection for small utility trailers, boats, or campers—everything most folks need for everyday towing.


Customer Satisfaction Score:
95% were satisfied with this product
5% of customers were not satisfied
Ratings & Reviews
This was not listed as an exact fit but worked perfect with my 2024 Nissan Frontier. It all plugged into the factory wiring. Made for a very easy instillation.
Worked right away
Everything was on time and fit like a glove. Easy tracking shipment. Well done etrailer
Surprised it came so quickly
Everything fit and works perfectly. Less than an Hour to install and complete the job.
Wiring harness fit my Nissan Xterra perfectly. Took about 15 minutes to hook everything up and the trailer lights all work as expected. Very happy with the harness, relays, and trailer connector.
Everything came as planned. The wiring harness worked perfect. The video made it very simple.
Right part for the right car. Order shipped the day I placed it, arrived earlier than scheduled. Combined with their numerous videos on installation, hard to think of a better service package out there. So easy, so simple. And for less than half what my local parts shop quoted (and didn’t have in stock)
I’ve got three emails confirming order, shipment and delivery.
I’ll be back when it’s time to wire up the Rogue.
The install was very simple - I did not have any issues- and the product performed exactly as expected.
Very simple install, plug and play electrical connections, very simple to use and very good quality product. Very happy it was put on in PA on Friday afternoon and hauled a uhal trailer to GA Saturday morning. Had 0 issues. Definitely a 5 star rating
Hook up was super simple
Great product! Wish I'd bought this first.
I wasted alot of time trying to get running lights on my Nissan Xterra pigtail. I had brake and turn signal only. Excellent customer service- Molly solved problem with this harness. Best of all - she saved me over $200.00 that Nissan wanted just to diagnose problem. If I can install this, anyone can. It only took 10 minutes and I had running lights.
Thank you
easy hook up, with a little utube help..
Perfect fit, works as advertised.
Took less than 20 minutes to install. Hardest part was finding the plug in the kick panel, and putting the trim back on in the cab.
This kit has exactly what my 2015 frontier needed. The pieces are good quality and everything for exactly as it should. The instructions were accurate and I was able to install everything, but some steps were a little vague and a couple of additional pics would have made them more clear. Additionally, a mounting bracket for the trailer connector would be a great addition.
Easy installation... the online videos really helped.
I had an existing harness that was installed with the hitch and the running lights were not working and the shop couldn't figure out the problem!
I removed the passenger side panel and saw the relays were missing. I decided to just tackle the fix myself and it worked out great.
I received my hitch and wiring harness kit for my 2019 Frontier within a few days after ordering. The items were well packaged, and nothing was damaged. The install instructions/video on your website were spot on. I had the whole thing installed and ready to go in less than an hour. Fit and finish of the etrailer hitch is very nice for the price. I would definitely recommend etrailer.com to others.
Got it very quickly. Installed within minutes. Thanks, Guys!
Super easy install! Does the intended job, thanks etrailer!
I have not installed this item yet, but I am sure it is fine. I had ordered this trailer wiring harness from a different seller. After 11 days waiting I cancelled the order and ordered from etrailer on a Monday. It arrived ahead of schedule on Wednesday and was exactly what I ordered, complete, and in good condition. I can't ask for more than that.
The job was exactly as instructions laid out. The customer service was excellent and the items arrived on time.
Worked perfectly
Plug and play.
The garage that I go to that fixes our cars said this is the easiest hitch he ever put on. The 4 pole connector was very simple to hook up too.
All of the wires fell out of the gray connector on the Flat 4 wiring while routing the cable. No excessive pulling, they simply fell out upon minimal tension. Curt must have had someone new on the line that day as none of the wires were terminated/crimped properly. The relays worked great and I could use those. Etrailer Customer service has been just a hair above useless since wouldn't even acknowledge the time sensitive timeline I was on and they could not do any express shipping to assist with a replacement, the replacement proceeded to show up 2 days after the expected date, well after my timeline. I sourced the flat 4 harness from somewhere else, returned their replacement along with the defective flat 4 harness. I've requested a refund for the portion I had to source elsewhere via email and hand written note in the return box itself. I simply do not get any response or acknowledgement of the request. What was supposed to be a 30 minute install turned into an afternoon of customer service calls/emails, attempting to fix the harness, sourcing of a backup, anxiety if I'd get everything sorted in time for my trailering needs, revisiting the install with the backup since they couldn't support me with an expedited shipment, a return shipment of the unused replacement that arrived too late, and now I'm receiving "leave a review" emails pretty consistently, so here it is. A review. Faulty Harness and a customer service team that doesn't communicate well or have the ability resolve a time sensitive issue.
I'm thinking I will source my trailering items from somewhere else.
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Mike L.
4/4/2026
Thanks Tim, I'm glad we could help!