The Check Engine Light: Out of Sight, Out of Mind

Jim Motavalli

Jim Motavalli | Mar 07, 2013

We've all had this experience, in one form or another. Driving along perfectly happily, maybe humming a song, and all of a sudden the "check engine" light comes on. Omigod. What does it mean? Actually, you can keep driving until it's convenient to seek professional help. But that darned light causes a whole lot of angst because people just don't know what to do, and meanwhile it's glowing at them like some kind of judgment from above. No wonder some people end up covering the light up with a piece of tape.

Panic time: It's the check engine light!My aunt called me today because a warning light had come on in the 2007 Toyota Corolla she bought new. She wanted to know what to do, and she wanted that light off. That’s nothing more than good ‘ol human nature at work. Good news! This post here tells you how to turn off the check engine light in a few minutes by jumping a fuse gap with a bent paper clip. But—and this is a big but—there's still an unresolved problem!

In truth, there are two schools of thought about check engine lights. One is to conclude that the powertrain is about to self-destruct and even driving another 500 feet risks not only severe bodily harm but the end of your car forever. The second is to focus on turning the light off. There are countless pages on the Internet devoted to turning off the check engine light. Check here, here and here. The thing is that the light’s always-on glare sends an irritating message—demanding attention, judging you, and interrupting your morning commute’s tranquil flow.

Ray Magliozzi is right with me on this. "The light is like having a telephone ringing, it's annoying," he said. "They come into the shop and say, 'Can you just turn the damn thing off--I'm tired of looking at it.' But, of course, it's good to know why the light is on. One reason people aren't all that interested in finding what's wrong is that their car is probably running fine. But if you have a bad fuel/air or oxygen sensor, you could be affecting the life of your catalytic converter. A bad thermostat, which can also turn on the check engine light, will prevent your engine from reaching operating temperature and affect both air quality and fuel economy. But unless people see their gas mileage go down by at least 40 percent, they don't notice it. I've had a lot of years of watching how people treat their cars, and most aren't that tuned in. Even if there's a noise, unless it's horrendous the tendency is to keep driving."

Kevin Nehez, a mechanic at my local Maier’s Garage in Bridgeport, Connecticut, confirms this view of human nature. "When the check engine light comes on, a lot of times people are more interested in getting the light to shut off than addressing the actual problem." Amen, Kevin. Of course, the check engine and other warning lights are controlled by sensors that aren’t always reliable, and Kevin tells me his sometimes come on when the thermometer drops below 10 degrees Fahrenheit. But, c'mon folks, unless you have an advanced degree in diagnostics, you're going to need a mechanic to decide what's wrong--the paper clip is only so effective.

When the check engine/airbag light comes on, get thee to professional help. (Flickr/JustTooHottoTouch)The easiest check engine light fix is not all that technical and spelled out clearly in the video below. All you do is…put a piece of duct tape over the light! There, fixed! My wife’s father did exactly the same thing (for a seatbelt warning light), using black electrical tape. My stepfather went the tape route, too, when that yellow beacon refused to extinguish itself. The Magliozzi brothers favor electrical over duct tape, but not as a substitute for fixing actual problems.

Let's take a big leap of faith here and assume that you actually want to address the underlying causes of the warning light coming on. Chances are it’s the result of an emissions problem and not a sign of imminent engine failure (that’s the oil light!). According to Consumer Reports, since the OBD II regulations went into effect in 1996, automakers have been required to install a system “that essentially acts like a built-in state emissions testing station.” The computer monitors dozens of processes, including emissions and the fuel system (for escaping gas vapors). That’s why a loose gas cap can set it off—check that first.

Things that can set off the check engine light are low fluids (oil, transmission or brake fluid, antifreeze), broken belts, a bad catalytic converter or non-functional sensors.

If your car has both red and yellow lights, and it’s the red one that’s on, it’s a more serious problem. You can drive with the check engine light on, but get it checked out soon. The computer will reveal a diagnostic code, which mechanics can read and then fix the problem. Then the check engine light will go out, without any need for your favorite kind of tape.

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