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Wiring a trailer can get messy fast if you have to splice into factory circuits, but this harness makes it simple. The Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector plugs directly into existing vehicle connectors. There’s no cutting or guesswork—just plug it in and run the included power wire to the battery. It gives you a solid, factory-style connection that’s ready to go.
Some factory lighting systems can’t handle the extra load from trailer lights. This harness solves that with its powered converter. The converter draws power directly from the battery, protecting the vehicle’s delicate tail light circuits from overload. It keeps everything working safely and reliably, even with fully lit trailers.
Once installed, the harness provides a 4-flat connector that powers your trailer’s running lights, brake lights, and turn signals. It’s the common setup for small to mid-size trailers and works right out of the box with most standard trailer plugs.
If you plan to add electric brakes or a 12V charge line later, this 4-way is an easy starting point. It plugs directly into 7-way adapter kits like the ETBC7 when you’re ready to upgrade. That means you can start simple now and add more capability later without redoing your wiring.
The included power wire runs straight to the battery for a clean and dependable power source. This setup keeps voltage steady for bright trailer lights and ensures there’s no battery drain when the harness isn’t in use. It’s built for worry-free towing every time you hitch up.
Customer Satisfaction Score:
95% were satisfied with this product
5% of customers were not satisfied
Ratings & Reviews
Product works as advertised.
the videos, available, help immensely in installation. Watch more than one, as some have helpful hints that others do not.
One such video mentioned the green wire, going to the right side, was barely long enough. I ended up, splicing the green wire to make it longer, after viewing more than one video. It made installation easier, since I also took an alternative route for the wiring.
Works great, used the rear cigarette lighter wiring for the power as trailer has led lights.
Jerald M.
2/11/2018
Still working fine , thanks !
I bought this for my 2015 Sienna and it worked great for a few years for some occasional towing. Then it suddenly stopped working. But I am convinced that the problem is not with the product rather with how it was installed.
I made the mistake of letting an auto mechanic friend of mine install it, thinking he would do a better job than I would plus I wanted to give him the work, but that was a big mistake--he either did not read the instructions or chose not to follow them. In either case, he installed the trailer attachment cable on the OUTSIDE of the car instead of the INSIDE. When I went to go rent a trailer, none of the lights would work and, after uncoiling the entire length of the cable, I discovered to my horror that the insulation had been worn through in several spots and some of the conductors were even missing. I saw some reviews of others who had decided to put the cable on the outside. My experience is that doing so is a recipe for the cable not lasting as long as you would want. I am buying another one of these to replace the one that was ruined and this time I am DIY so that it is done right.
Product in use for 1 year. Product works well without issue. Installation instructions were clear and very good, and customer service has always been very good. I hope the company stays around for my future automotive needs.
James
1/7/2019
Wiring is still going strong. Good customer service. Nice doing business with them
Hitch went on easily. And the wire harness was simple. Just watch the YouTube videos to better understand the whole install. I ran the power wire through the cabin and the a grommet in the fire wall of the driver side. Took a little more time but I thought this was a better way to route instead of under the sienna.
Mike
7/25/2015
Thanks, Moses. Can you elaborate on the in-cabin route you took for the wiring. I would like to attempt. I cant imagine running it under the car without a lift!
I made a mistake on my order and had to return the first one. The ordering info. wasn't very clear for my Sienna. However, when I got the correct unit it went right in. I found it helpful to watch a couple of [online] videos before I did the install. I couldn't be happier with the way it all came out and how well it works!
Stephen S.
12/16/2024
I installed the wiring harness a year ago. It has and is working flawlessly! Im very happy that I was able to install it myself and that it continues to perform so well!
Running the power wire to the battery is difficult. The controller on the first Curt wiring harness died on day one when I went to go pick up my boat. I had to drive for over an hour with malfunctioning trailer lights. The defective harness was replaced under warranty and so far so good but having to install the harness twice was a hassle.
Jay O.
7/4/2023
After one year of use the replacement Curt wiring harness is still working. Id change my review to 4 stars if I could.
The first Curt harness kit I installed failed the second time it was used. Parking lights came on all the time and right side stop and turn signals didn't work. I ordered another new Curt kit (paying $30 less) and paid to ship the defective unit to etrailer. The second kit has been working so far. Instead of issuing a refund for the defective item, etrailer shipped me another Curt harness kit. At least this time etrailer paid for return shipping on the kit I didn't need. After paying for two Curt harness kits, paying return shipping on a defective kit, dealing with an unwanted kit, I finally received a credit to my account for the original order. It shouldn't be this difficult. I will give etrailer customer service a thumbs up for good communication or the rating would have been 2 stars.
Jay O.
11/6/2022
After one year the Curt harness kit for Toyota Sienna has been working as advertised.
Installation was pretty straightforward and was well demonstrated in the installation video received in the email. I am not very handy, but was able to finish the installation myself by following the video. The most difficult part for me was raising my Sienna so I could get underneath to work. The provided sticky pad was totally not sticky at all. I was a little disappointed, but it was not a big deal.
About inserting the black wire through, rather than drilling a bigger hole and sealing it later on, I just removed the rubber cover, drilled a little narrower hole on it, put the black wire through and put the cover back on.
After passing the fuel tank when wiring the black wire from back to front, I removed the cover mentioned in the video, then wired the black wire through. It would not be easy without removing the cover, and it was very easy to take it off and put it back on with a 10 mm socket and a drill.
A spare wire connector in the kit would be better. Also an optional four-way trailer light tester in the kit will also make it more convenient.
J.l.
10/29/2022
It has been a year since the installation. I only tow occasionally, but every time it reminded me of a good purchase I made. My colleague liked it too and was impressed that I could install it myself They know I am not a big guy and not that handy. I strongly recommend spending some extra bucks on this hidden-behind-bumper model. The reason is aesthetic for sure. This kind of feeling can add up over time as most of the time I only see the ball mount. Last week I got a rear flat tire on the highway at night. My trailer hitch ball mount was attached at that time. There was no problem when the tow truck driver drove my sienna onto his tow truck. When he wanted to back it off his truck. The ball mount caused a problem so he had to make some kind of ramp on the flat tire side. Taking off the ball mount may be a good practice when not towing. But who knows what can happen before you do it. In my case, a unhidden hitch will just make a bigger problem.
Tedious, but doable. Just take your time. Great install, seems robust and sound. Would be nice if I had a lift, but who’s got that?
Quality products at competitive prices with good customer support. The online videos were great, and showed step-by-step for my exact installation & vehicle.
Great service - thank you!
I’m giving this two stars only because of poor service from trailer. I ordered from my phone and didn’t notice the unit I ordered was for a different model Sienna. I had to pay to ship it back to get the correct one. I got no sympathy as it was my fault that the site wasn’t as clear as it should have been according to the woman I spoke to. Once installed it worked well. As I was annoyed I bought my Thule XL rooftop cargo box at (another store) (at a better price too)
Love the look. Installer said it was straight-forward and presented no problems on our Sienna. Wiring harness stays inside car (away from weather)
so it saves wear and tear and retains clean look.
Awesome people. Awesome company.
Thank you Andy!
Good quality product
Doug
3/24/2026
It worked out great for the only time we needed it to.
Gwendolyn Y.
3/24/2026
Was professionally installed and only made it on my vehicle 9 months with minimal use. Brake lights and blinkers no longer work after a minute or two leaving me with just tail lights at night. If I'm forced to tow something I have to flip my lights on when braking for safety.
The harness works well. The instructions leave a lot to be desired. I didn't realize by reading the instructions that the module was supposed to be mounted on the drivers side. I figured it was like the etrailer harness I mistakenly bought before. However, it reversed my turn signals.
I just installed the Curt hitch and wiring harness for my 2015 Sienna XLE. This was without a doubt one of the easiest and most straightforward installations I've done to date on numerous vehicles. I ran the power wire in the cabin. I just tucked it along the carpet and paneling on the drivers side, then I drilled a hole larger than the wire to the drivers side of the steering column boot. Ran the wire up under the carpet behind the brake pedal and then out into the engine bay. Great products!!
Was not difficult to install
Exactly as described. Fit my vehicle perfectly. Can't go wrong with the detailed instructions and videos per vehicle year too!
Everything excellent as expected. Very quick shipping.
Good kit. If it had a water sealed connection at the battery I would have given it five stars.
Easy install, watched the e-trailer vid eo.
I attached 3 pictures showing the routing of the trailer wiring on my 2015 Sienna.
I purchased the Curt trailer wiring harness about 2 yrs ago. I didn't like having it running out the back hatch. I use my trailer a lot. I purchased the Curt 58001 mounting brkt. I reviewed the wiring install video and saw the grommet that you normally use for the power line to the harness from the battery. Now I had the hole to run the trailer connector wiring thru with out make another hole and having to splice the connector wiring.
I cut a slot in the middle of the grommet for the wire and then continued to cut the grommet so I could slip the wire to the center of the grommet, put on some liquid electrical tape and ran the wire to the bracket. As waterproof as original. Mounting bracket made a nice, practical connection point. I greatly appreciate your videos and etrailer is my go to source.
Mike L.
4/24/2018
On vehicles like passenger cars and minivans that arent typically used for full-time towing, the wiring harness manufacturers specify an installation that keeps the trailer connector inside the vehicle where its protected from the elements. Theres no problem with the way you installed the harness, but be aware that the connector is not as protected against corrosion caused by moisture and exposure to road debris.
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Keith M.
10/12/2019
Great!!!