SK Crowbait

Hey Guys,

I was changing out my idler pulleys today and found I had a 4 pin plug just hanging loose below my fan cowl right near the oil filter. I have my oil changed by a shop, so I not really down the often, but the Son saw it dangling from where he was looking down from up top. I crawled around and couldn't see where it was meant to be plugged in to. I have no error codes, and no obvious problems with the truck. Any idea what it could be? I bought the truck with 40,000 miles on it 6 years ago and never noticed that plug hanging there, but that's not to say it hasn't always been that way, other than its not very dirty.