Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
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2020 Mazda CX-3
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2020 Mazda CX-3
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Wiring a trailer doesn’t have to mean tapping into factory wires. The Curt T-Connector with 4-pole flat trailer connector plugs inline with the vehicle’s existing tail light wiring. There’s no cutting or soldering — just plug in the connectors and it’s ready to go.
The harness provides a standard 4-flat connector that handles running lights, turn, and brake signals for most small and medium trailers. It’s the basic setup you need to safely tow utility trailers, campers, or boat trailers with working lights right out of the gate.
A built-in powered converter isolates the trailer wiring from the vehicle’s sensitive electronics. If there’s a short on the trailer, it protects the vehicle’s circuits by absorbing the fault instead of passing it upstream. This keeps the factory system safe and prevents costly repairs.
If you ever move up to a larger trailer with electric brakes or onboard charging, this 4-way harness can be expanded using a 7-way installation kit such as the ETBC7. It connects right to this harness so you can add brake control wiring and a 12-volt power feed without redoing your entire setup.
Each wire in the 4-flat connector corresponds directly to a light function — yellow and green for turn signals, brown for running lights, and white for ground. That makes testing and tracing any issue straightforward with a simple circuit tester, so you can diagnose and fix problems quickly.
Customer Satisfaction Score:
94% were satisfied with this product
6% of customers were not satisfied
Ratings & Reviews
Greg
6/12/2023
After a year, no issues. Harness still works fine. Not had any issues with lights working once plugged in.
Mike L.
7/12/2023
Ralph
3/24/2022
works great
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Evgeny
4/11/2025
1 year later still working as intended, survived Canadian winter.