What would cause my 2016 FIAT 500X check engine light to come on?

The reason why the check engine light might be on in the 2016 FIAT 500X could be because of any number of reasons. Some of the main reasons could be from a faulty oxygen sensor, a loose or broken gas cap or from bad spark plugs. All of these problems are pretty easy and cost next to nothing to fix. If the problem is from a bad or loose gas cap You can try to tighten it to see if that fixed it or if it is bad/broken You can buy a new one for around $10 to $20 or so. If the problem is from a bad spark plug You can get a new one for around $8 to $20 or so.