How and Where to Wire the Four Loose Wires on the 4 Pole to 7 Pole Adapter, part # 30717

Expert Reply:

The white wire is a ground and should be attached to the frame. The blue wire goes up to the blue wire on the brake controller. The black wire is a 12 volt power wire and is connected to the car battery. The orange or yellow wire can serve a few functions. It can be a reverse lockout for hydraulic brakes, it can be an auxiliary power supply, it can be used for reverse lights on a trailer, or if not needed, it can be taped out of the way.

I attached an FAQ page on brake controller wiring to the right that you should find informative.

expert reply by: Patrick B