Why is my Ford Mondeo's check engine light on?

I just purchased a used Ford Mondeo and the check engine light keeps turning on. What could be causing this and is it something I should be worried about?

One possible reason for your check engine light could be a loose gas cap. Make sure it is tight and see if the light goes off.

It could also be a faulty oxygen sensor. I recommend taking your Mondeo to a mechanic to get it checked out.

My Ford Mondeo had the same issue and it turned out to be a faulty mass air flow sensor. Make sure to get it fixed as soon as possible.