What is this?
 

I was driving home from work and i got this. I don't know what it is. I tried searching it but i don't even know where to start. What is it?
https://cimg3.ibsrv.net/gimg/minicoo...416dcf88cd.jpg

First thought was a loose gas cap.

Yeah thats what my buddy told me. Turns out, it wasn't loose per se, the rubber wire (which is now ripped) that is attached to the cap and the car, was caught under the cap and maybe the sensor picked it up as "loose." Fixed it so hopefully that was it. To me, it looked like a screw or something. And my gas cap is on the left side so it confused me a little.