What pin is this?

[Chamberpains]

It can be the problem only if its supposed to go to something. They do run harnesses with dead ends or not used leads. You'll have to get a wiring diagram of your truck to see what or where that lead goes if anywhere at all.
You can google search your truck year and model with wiring diagram and you'll probably find someone has posted it somewhere or they sell them on some other sights. They are very good to have if you do a lot of your own work.