Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
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2023 Mercedes-Benz GLS
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2023 Mercedes-Benz GLS
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Hooking up trailer lights doesn’t have to mean cutting into factory wiring. This Curt T-Connector plugs directly into the tail light connectors, so you get a clean 4-flat trailer plug without splicing a single wire. It’s a plug-and-play setup that keeps things factory-looking and reliable.
The built-in powered converter draws power directly from the vehicle battery instead of the tail light circuit. That protects sensitive electronics while giving full power to the trailer’s running, turn, and brake lights. It’s designed for steady light output and dependable performance across different trailer setups.
With connectors that plug in right behind the tail lights, the install stays simple and accessible. Mount the converter box on a clean surface, run the included power wire up to the battery, and you’re set. The self-tapping ground screw and fuse holder make it easy to finish the job with basic tools.
Once installed, you’ll have a standard 4-way flat connector that powers your trailer’s running lights, turn signals, and brake lights. It’s the common setup for small to mid-size trailers and pairs easily with 7-way adapters when you’re ready to step up to more advanced towing gear.
Customer Satisfaction Score:
91% were satisfied with this product
9% of customers were not satisfied
Ratings & Reviews
Perfect
Great product and best price found after shopping around. Items were delivered quickly and professionally wrapped. Obviously this company cares about their customers. Kudos you have a new customer for life.
Item worked well. Was able to run all wiring inside my 2022 corolla cross L AWD
Plug and play 100%
Very good product, perfect fit and easy installation.
Both the heavy hitch receiver and wiring kit came nicely packed, undamaged with all parts necessary. Installation, while a bit complicated to remove the plastic trim, is straightforward on my Toyota Cross, a simple bolt-on swap with the factory steel bumper, eight bolts, and a small trim before reinstalling the plastic cover.
We installed this wiring harness while we had the bumper cover off to install the Curt towing hitch for the Corolla Cross. That made installing the harness a breeze. We simply zip-tied the cables to already existing wiring, slipped the hot wire to the battery (in the hatch on the hybrid Corolla Cross) through the rubber grommet under the right taillight, and brought the four prong trailer plug down right alongside the hitch. We tested all the car and trailer lights before reassembling everything, and they all worked perfectly. Note we have the Corolla Cross Hybrid SE, which does not have LED taillights.
We installed a hitch at the same time as this connector kit. It was pretty easy but do recommend having a 4 pole flat tester to plug in if you don't have actual trailer lights to test the setup before the bumper cover goes back on.
Hooked this up on our 2025 Toyota Corolla Cross hybrid. I really like how this harness connects to the car’s wiring through plugs in the taillights. Biggest challenge is running/securing a controller power wire to your car’s battery. But with this particular vehicle, starter battery is in the back. Nice!
Everything arrived in a box in good condition and timely and i didn't even open it. Just handed the box to the installers and everything they needed was inside the box. Very satisfied.
Power wire to battery too short, did not reach battery by 2 feet.
Flat four wire to trailer was short, restricting placement of controller box.
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Jake
6/26/2024
1 year later - still works great. Happy with the product.