On my 1996 318, there is a small black box that sits on top of the alternator. There is a wire coming out of it that ends in what looks like should be a ground ( a small circle with teeth on it). It is just hanging there, not plugged in.

Anyone know where (or if) this is supposed to be plugged into?

The truck is running fine, with no issues, by the way.

 

That is a ground cable, looks like it could go on that bolt in the picture you have, run it around to see how far it reaches and ground it on the manifold bolt that it reaches.

 

I just went and look on my truck to be sure and that stud in the picture is where mine is grounded.

 

Great, thank you for checking it out. I will get it done tonight. It's weird that there was no issue having it unplugged. It's been that way the entire time I've owned my truck, as far as I know.

 

It is most likely a back up ground or a multi fit Alt. but either way, it ought to be grounded as GUZMAN said.

 

It's not unplugged, it's just a ground....I'd extend the wire and run it to something like the frame or engine block, or better yet the - post on the battery.