In this tutorial, we learn how to check the engine light. The check engine light comes on when the engine control module recognizes that your car emissions are not running properly. All of the systems work together with sensors to make sure everything is running correctly. Some problems can be severe while some won't affect the way to car drives at all. When you take your car into a mechanic shop, they will hook it up to a computer which will pin point what the area the problem is in. So make sure you take your car into a mechanic shop when the light goes off, it could save you a lot more money to get the problem checked out early.