Wiring Adapter for 2012 Lexus GX460 with 4-Pole Wiring to Match Trailer with 5-Pole Harness

Question:

I have a Lexus GX460 that has the factory trailer wiring plugs installed. There are 2 connections. The first is one for a flat 4 wire connector and there is one for the round connector. The new trailer I purchased has a flat 5 wire connector, to activate the brakes. Is there a plug available to accept the flat 5 wire plug that would connect to the round factory plug-in?

asked by: Ron

Expert Reply:

There are several ways to go about wiring together your vehicle and trailer that have different type connectors.

We offer Tow Ready 4 Pole to 5 Pole Trailer Wiring Adapter # 20036 that connects to the car's 4-pole, and which provides an additional (blue) wire-lead to carry a trailer brake signal to the trailer's brakes. This extra blue wire would need to be connected to the car's brake controller output signal. This signal is not carried on the 4-pole flat connector so you would need to tap into that circuit on the car's 7-way round connector. In a typical 7-way socket the pin that carries a brake controller's signal is located at the 5-o-clock position as shown in the linked photo.

Another (better) option is to re-wire the trailer to match the vehicle's 7-way. This avoids adapters and the extra connections and potential problems they can introduce. You can add a 7-way plug # H20046 by mounting a wiring junction box # 38656. The existing trailer wiring and the new 7-way plug will be joined inside the junction box using ring terminals # 44-5310A (you'll need 10).

Trailer and vehicle wiring colors are not absolutely standardized so it's best to test the vehicle harness with a tester like # PTW2993 and to test the trailer wire functions using the car's battery or a spare battery. To test you'll disconnect the trailer from the car and test the pins on the 7-way socket to confirm what function is carried on each contact. You'll apply 12V power from the car battery one at a time to each circuit on the trailer connector to confirm what each wire does and then match up the two harnesses inside the junction box.