It happens at the worst time - stuck in traffic or a long road trip - when you see that check engine light flick on. Here's why it may keep returning.

Remember, the code reader won't tell you how to fix the check engine light—the code it reads just directs you to the fault. From there, unleash your mechanical prowess and discover the cause!

Although most check-engine malfunctions will require a code reader to diagnose, something simple to try is to make sure your gas cap is tightened — particularly if the light came on just after ...

With a code reader you might find you can simply turn off the check engine light yourself. However, if you haven’t fixed the problem, it will eventually come on again.

Discover what an OBD2 scanner is and how to use it to diagnose and fix car problems before they escalate into major repairs.

Having a hard time interpreting the car codes your dashboard is displaying? Car codes can be confusing, so here are the best OBD2 scanners for reading, analyzing and clearing diagnostic trouble ...

If you see the check engine light and haven’t filled up with fuel recently, it’s a good idea to use a code reader or take your vehicle to a shop for diagnosis.

Do 'check engine' codes mean Camry needs new catalytic converter? Q: I have a 2003 Toyota Camry with the "check engine" light on. A code reader shows codes PO430 and PO420. How should I proceed?

Consumer Reports explains what the check engine light means and what to do when you see it: how to tell if your car has a loose gas cap—or a serious engine problem.