Trailer wiring help - NEED ASAP.

[Ed]

Hey guys-

I recently bought a used TAHOE with the tow package. There was not a wiring harness on the truck so I went down to UHAUL and told them my make, model, year and they sold me a 4 way flat plug (with the indicator lights to let you know everything is connected okay). So,I wired it to the rear of the truck and everything seems to work okay. Here is the problem.....when i went to connect it to one of the boat trailers at work...the trailer had a 5 way flat plug and my plug on the truck is a 4 way flat. UHAUL says they don't make a 5 way flat plug. I am assuming that the fifth plug on the trailer is for the reverse lock-out actuator.

Here is my question....I want to create a separate wire to connect the reverse lockout actuator on the trailer to the wiring harness on the truck. What wire on the wiring harness do I connect it to? The green, yellow, white and brown wires have all already been connected to the 4way flat plug.

Any advice would be most helpful.

Ed