Your check engine light can come on from anything as simple as a gas cap to an electrical failure and everything in between. The only way to know why it's on is to have a diagnostic test performed to find out why and what needs to be done to keep you on the road. This is not the same thing as a quick scan. While a quick scan is convenient it will not always tell you what the problem is. Let's say you have a misfire code. This you would think means that you need new spark plugs and this could be true, but what if you just had a tune up and this is now coming back. Your spark plugs are probably fine it most likely an issue with one of the other ignition components. This requires a test to find out which one it is. I wouldn't want you to go through the process and expense of another tune up when it's not needed. Give us a call and let us take care of you.