ANYONE KNOW WHAT THIS IS

I found an interesting plug up behind the left rear tire, it had a grey blank in to keep it clean. It's not used, not that I can see and it looks factory. All lights work.

it could for trailer lights, thats probably the fatory plug and when u buy the truck new and add the option of a hitch and charge 500$ they plug it in there plug and its ready to go

Looks like it's a mate for this:


An OEM trailer connector

yep that's what it is