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Getting trailer lights wired up usually means cutting into your vehicle’s wiring, but this harness skips all that. The Curt T-Connector plugs inline with the tail light connectors to give you a 4-flat trailer plug. There’s no splicing or guessing which wire does what—it just clicks into place and you’re ready to go.
The powered converter in this harness keeps the vehicle’s factory circuits isolated from the trailer’s wiring. All trailer light power is drawn directly from the included 12-volt lead that runs to the battery through an inline fuse. That means a short on the trailer will blow the harness fuse instead of damaging your vehicle electronics.
Whether your trailer has standard bulbs or LEDs, this setup keeps everything working like it should. The converter provides the correct signals for running, brake, and turn lights through a 4-pole flat connector that resists corrosion and maintains a solid ground connection.
The harness connects behind each tail light—yellow wires on the driver side and green on the passenger side—so everything lines up easily during install. Once plugged in, the converter box tucks neatly out of sight for a clean finish that won’t get in the way of cargo or trim panels.
If you ever step up to a trailer with brakes or need a 7-way plug, this 4-flat serves as your starting point. Just add an adapter kit like #37185 or #ETBC7, and you’ll have all the circuits you need for a fully equipped towing setup down the road.
Customer Satisfaction Score:
91% were satisfied with this product
9% of customers were not satisfied
Ratings & Reviews
Victoria H.
3/19/2025
That's good to hear we were able to help you get this sorted out Michael! We appreciate you taking the time to share your insight.
Rachael H.
9/25/2017
It is strongly recommend to run the 12 volt power wire directly to the vehicle battery. The 12 volt accessory circuit was not designed to support the additional load of a trailer wiring harness. A wiring harness must have its own dedicated circuit directly to the battery. We have seen many instances where customers have tapped into a 12 volt accessory circuit, like a car lighter socket, and the harness failed. We have also seen instances where the accessory circuit on the car failed in addition to the trailer wiring harness. Also, this will typically void warranties both with the wiring harness and on the vehicle. For more help with routing the wire, see this helpful article found at: https:/www.etrailer.com/faq-Routing-a-Power-Wire.aspx
Jed
9/21/2018
One year out and Im totally satisfied. Everything just WORKS every time.
Patrick B.
3/27/2014
The video we have is for the Tow Ready harness designed for the Sienna. Though the harnesses install very similarly, the converter box mounts in difference locations. With the Curt harness the box mounts behind the driver side tail light. The Tow Ready kit, part # 118498, mounts the box inside the passenger side jack storage compartment in the cargo area.
Ima K.
7/17/2020
Still working as good as day one. I only use it about 10 times a year for towing a small motorcycle trailer, but havent had any issues. I can always just plug it in and go.
Len
6/9/2014
All is working great, will certainly shop again when looking for trailer related items, and will enthusiastically recommend etrailer to anyone needing the same.
Jimmy
11/16/2018
The wiring harness continues to be very dependable, a quality product.
Juan T.
4/28/2014
The company service was great and the item was as described. This is not a bad review or anything but it took me 6 months to use it for the first time just to find out that the signals where indicating the wrong turn. I guess that all I have to do is fix the wires.
Patrick B.
5/5/2014
Patrick B.
10/30/2014
Tapping into a power source at the rear of the vehicle is not recommended. Not all of them are only hot with ignition. Furthermore, its usually unknown exactly what else is on those circuits so a short on the trailer would overdraw that whole circuit taking out whatever else is on it. Perhaps most importantly, is the goal behind the power wire itself. The idea is to separate the power draw for the trailer lights to its own feed. This protects the vehicle. If you splice into another power source rather than running that wire as a dedicated feed, youve defeated the purpose.
Mike
3/12/2021
Its been a year and still going strong. This item is built to last.
Mike L.
8/7/2018
According to Curt, theres been an internal short in the converter box, which is what is causing the problem you mentioned. The vast majority of the time, when a taillight converter shorts out its been caused by a short circuit somewhere in the trailer wiring or a damaged trailer connector on the vehicle or the trailer. Id recommend closely examining the trailer wiring, beginning at the trailer connector and working your way back to each lamp. Look for pinched or broken wires or loose connections. Check for cracked or worn wire insulation that would allow the copper conductor inside the wire to short out on the trailer frame. Ill link you to a help article on troubleshooting trailer wiring which will be helpful.
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Daniel
7/28/2021
After using the wiring harness for a year its still working out well for me. I just used it last week with a cargo carrier and the lights were still working well. Ive used it about 4 times this year and when its not in use it tucks nicely into the 8th seat compartment so its not really in the way during normal use.