Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
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2020 GMC Sierra 1500
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2020 GMC Sierra 1500
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Hooking up trailer lights doesn’t have to mean cutting into factory wires. The Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector uses factory-style plugs that fit right into the rear light housings. Each connector snaps in with a solid click so you know it’s fully seated. It’s a plug-and-play setup that gets you towing faster with no guesswork about which wire goes where.
This harness comes with a powered converter that connects straight to the vehicle battery. That power line isolates the trailer lighting circuits from the vehicle lights, so the trailer lights draw their own power instead of loading the vehicle wiring. The built-in fuse adds circuit protection, and in case of a short on the trailer, only the converter or fuse would blow—not the vehicle electronics. It’s simple peace of mind every time you tow.
The 4-flat connector gives your trailer running lights, turn signals, and brake lights through standard pins that match most small and midsize trailers. It’s a clean, weather-resistant plug that tucks neatly near the hitch for easy access whenever you need to hook up.
Good lighting starts with good grounding. The white ground wire is designed to mount to a clean, bare metal surface—no paint or rust—to ensure stable current flow to the trailer lights. Tight fittings and weather-protected connectors help keep corrosion out and signals consistent so your trailer lights work when they should.
Customer Satisfaction Score:
95% were satisfied with this product
5% of customers were not satisfied
Ratings & Reviews
Mike L.
5/28/2026
You can always use the link on our product page that'll take you right to a .pdf with clear photos. I'll link that for you.
Helpful Links
Jimbo
5/29/2018
I have absolutely no problems with all purchases equipment. Works as advertised! Thanks for caring enough to follow-up a year later.
Mike L.
8/22/2018
Typically, a taillight converter shorting out is caused by a short circuit somewhere in the trailer wiring. Id recommend very carefully examining the wiring on the trailer. Begin at the trailer connector, look for corrosion or for damaged pins. Check the point where the wiring meets the 4-pole plug, its a common failure point. Trace each circuit rearward until it connects at its fixture. Look for loose connections or for bent or pinched wires. Make sure theres no cracks or worn spots in the trailer wiring that would allow the copper wire to short out to the trailer frame. Make sure the connection at each lamp is secure. If the short isnt located and repaired, each subsequent taillight converter thats installed will continue to short out. Ive linked to help articles that explain various troubleshooting strategies.
Heather A.
5/1/2026
That’s definitely frustrating, especially with a plug-and-play setup like this. If the brake lights aren’t working, it’s usually tied to the power or ground side of the harness rather than the connectors themselves. This kit uses a powered converter that needs a solid connection to the battery, so it’s worth double-checking that the power wire is hooked up correctly and the fuse is installed. Just as important is the ground make sure it’s attached to clean, bare metal with no paint, rust, or coating underneath, since a weak ground can cause brake light issues. It’s also a good idea to confirm the T-connectors behind the tail lights are fully seated, since they can sometimes seem connected when they’re not fully clicked in. If your running lights and turn signals are working but not the brake lights, that can help narrow things down further.
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Mike L.
7/16/2026
It's really important that you draw the 12V directly from the battery. This totally isolates the vehicle's wiring system from any short circuits that could occur in the wiring on the trailer. If you have access to ramps and a floor jack/jackstands you can lift the rear of the vehicle and run the wire as far forward as you can, then lift the front and finish the run. If you decide to go that route, be sure to chock your wheels!