Check Engine Light: What Is Your Car Actually Telling You?

When the check engine light comes on, your vehicle's computer has stored a trouble code. That code identifies the system or circuit where a problem was detected.

It does not, on its own, tell you which part to replace. An oxygen sensor code can be caused by a bad sensor, a vacuum leak, a failing catalytic converter, or even a loose gas cap.

That's why we diagnose before we recommend. Reading the code is the first step, not the last one.