The Toyota factory trailer brake controller plug on my 2005 Tundra has five wires but the brake controller uses only four of them and to make things difficult, none of the colors match up. Only Toyota would think of using a red wire for the output to the trailer brakes, when the industry standard calls for a blue wire. The printed instructions that were packaged with the wire harness shows that the unused green wire is from the “headlamp switch to vehicle TRAIL lamps.” Yes, I checked the spelling twice. What exactly are “trail” lamps or is it the printer’s idea of a Japanese joke? The use of a green wire to the tail lights makes more sense but I can’t think of any use for a wire to the trailer brake controller from the headlight switch. What am I missing?