My wiring diagram on the cover of my hitch plug says that the center pin is for Backup lights but i can't seem to get 12 volts from this pin, all the fuses are good and i don't see anything obviously wrong with the wiring.
I checked 2 other F-150's and found the same thing wrong
does anyone have a solution?
Is it something i'm overlooking?
I know that it can't be coincidence that 3 trucks are not working.

 

There is supposed to be a relay for the backup circuit in the power distribution box under the hood. The diagram should be in the owner's manual.

 

Also see this link for a related answer.