Why is the check engine light on in the 2017 ford expedition?

When the check engine light comes on in the 2017 Ford Expedition it means there is some sort of problem going on, either something minor or something major. It can mean things such as the O2 sensor needs to be replaced. The gas cap is loose or missing, the catalytic converter needs replaced, a problem with the mass airflow sensor or a problem with the spark plugs. Some of these issues cost nothing, cost little or are very expensive. You can either get a scanner and scan for error messages to find out what is wrong or just try to fix the simple things on Your own. You can tighten the gas cap to see if that is the problem. Or You can replace the spark plugs which are pretty cheap and easy to do. The other things that might be wrong with it are more complicated and more costly.