I have 1999 Ford F-150 xlt and on the passenger side the brake and turn signal don't work but reverse light does. On the drivers side everything works so I switch bulbs and outlets and it still doesn't work but two of the wires for trailer hook up and cut. I was wondering if that had anything to do with that.

 

Usually all the wiring is in a harness coming back on the driver side to the rear lighting.
If you see things are not hooked up, do it to it and see.
Good luck.

 

I checked the wires going to the passenger side and there is no short and I even took the ground off and used sand paper to get all the rust off to make a good ground. It still doesn't work.