Using 4 to 5-Pole Trailer Connector Adapter # 20036 for Towing Boat w/ 2011 Toyota Highlander

Question:

I have a flat four adapter on my car, and a five pin flat connector on my boat trailer. Is there an adapter?

asked by: Joe W

Expert Reply:

The extra pin on your boat trailer's connector is most likely a reverse lock-out for your surge or hydraulic trailer coupler. The extra circuit is tied into the reverse light circuit of your vehicle. When the vehicle transmission is shifted into reverse, the reverse light circuit energizes and activates a solenoid in your coupler, which allows you to back the trailer without the brakes applying.

We do indeed have an adapter that would work for you, part # 20036. The extra blue wire on the vehicle side will tap into the reverse light circuit on your Highlander. Access the rear of your taillight assemblies, like you would if you were replacing a burned out bulb. Find the reverse light bulb in the taillight assembly (It's the bottom bulb). Have a helper put the vehicle in reverse (with the brakes on!) and use a circuit tester like part # PTW2993 and probe the wires in the harness feeding the bulb until you find the wire that lights the tester. This is the wire you'll need to tap the extra wire from the adapter into.

I've linked to a video showing how to use the circuit tester.

expert reply by: Mike L