I have a 2007 Expedition with a flat four wire trailer plug. I bought a boat with a flat 5 wire plug and it has a reverse solenoid. I started to change out the four wire plug to a five wire plug but the blue wire which was taped to the harness wiring is not hot. I checked all the relays and fuses under the hood and in the fuse box and all are correct. Is there something else to do or to check? Thanks.

 

I believe to get the back-up lights, you have to tap in to one of the trucks back-up's and run a wire from there.....

 

The blue wire is probably the brake controller wire. It goes to the brake controller connector under the dash.

Unless there are other wires down there for 12V power and backup lights, you'll have to run those separately.