Does the check engine light actually indicate a problem?

Dear Car Talk

Dear Car Talk | Nov 01, 1989

Dear Tom and Ray:

My question concerns my 1987 Chevy Cavalier. The "check engine" light comes on all the time. I check the items under the hood that would cause this trouble and find nothing wrong. What should I do?

TOM: Some historical perspective is important here, Art. The "check engine" light originated in New York City many years ago. There was a wave of incidents in which car thiefs were stealing engines, and then re-selling them. The "check engine" light was invented as an indicator to the driver that the engine may be missing, and that the hood should be opened to see if it's still there.

RAY: But these days, the "check engine" light has developed into a much more sophisticated warning system. There are many sensors in and around the engine that are attached to a computer. When something malfunctions, the "check engine" light comes on, and the computer stores the information. The problem may not be something you can see, so don't expect to be able to diagnose it by looking under the hood.

TOM: What you have to do is bring the car to a mechanic and have him tap into the computer. With a tester, he can read the "trouble code" and tell you what's wrong with your engine. For instance, if the light flashes nine times, then pauses, then flashes two times, that's a code 92--it means your loan payment is three weeks overdue and your car AND engine may soon be missing!

RAY: But seriously, Art. Have it checked properly. That warning light could indicate serious trouble, or trouble that could get serious if you don't take care of it in a timely manner.

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