I have a 2009 F150 Platinum, I found the plug pictured near the spare tire it has 2 wires and is caped off and NOT jumpered. does anyone know what it is???

 

What Color are the wires?
I am almost thinking it could be for a cap, wire for the brake light and one for the interior light. 3rd brake light wire on mine is blue with a red strip and the dome light wire is yellow with a green stripe