What are the Trailer Wiring Color Functions on a 4-Way
Updated 12/22/2025 | Published 10/17/2024
Question:
I have trailer hitch I bought a few years back but have not had a chance to use it yet. I recently tried hooking up to a trailer but the lights are not working. When I bought the hitch I also got the wiring adapter for our 2017 Mazda CX- I just tested the output from the car and was hoping you could verify what I am seeing is correct. Between ground white wire I am seeing 12v on : Green - left blinker on Yellow - right blinker on Brown - head lights on I never see 12v on brown wire when brakes are pressed with head lights off. With head light on, I don’t see any change to indicate the brakes were pressed. On trailer, I see only faint illumination for the blinkers. Nothing for when brakes are pressed. Not positive on what happens with head lights on since when I tested the connection I think the headlights were on Auto and it was day time. I was mostly focused on having brake lights. For the trailer wiring I have white to chassis, green to left, yellow to right, brown is split from connector left and right. Does any of this seem correct? I welcome any input.
asked by: David S
Expert Reply:
Hey David, it sounds like you have it pretty close but not quite. The green wire should carry the right stop/turn signal, the yellow carries the left turn/stop, and the brown wire the running lights.
So the yellow and green would have voltage when the brakes are pressed and also intermittently when the blinkers are put on.
Product Page this Question was Asked From
etrailer Rubber Hitch Cover for 2" Trailer Hitches - Qty 1
- Hitch Covers
- Misc Covers
- Plain
- Rubber
- Fits 2 Inch Hitch
- Standard
- Square
- etrailer
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Jameson C.
12/22/2025
Hey David, how did things turn out after you corrected the wiring for your Mazda’s trailer connection? Were you able to get the brake and turn lights working properly on the trailer? Your results could really help others sorting out similar wiring issues.