When the "Check Engine" light turns on, you usually have to take it to a mechanic so they can diagnose the problem and reset the light. Sometimes the problem is as simple as forgetting to screw your gas cap tightly enough. Other times the problem is a not a problem but a glitch and the light stays on anyway. Instead of spending time and money taking your car to a mechanic, ">this scanner will tell you what the problem is and allow you to reset the "Check Engine" light. I have a Bluetooth scanner that connects to a phone app, but this is a simpler solution -- just plug in and Google the diagnostic code. And it's just $11 on Amazon.