You’re driving down the road when you notice it – Your check engine light is illuminated on your dashboard, causing a growing worry as you wonder what it could mean. What if it’s something serious? How long do you have before something breaks down? And, oh my God, will it be expensive? It’s this last question that tends to make people panic. So what do they do? They figure they’ll save some time and money, and they head over to the auto parts store for a free “check engine light test.” I’d like to explain why this is such a bad idea, and why you should head over to your licensed mechanic instead.