Top News

Figuring out what’s hiding behind that ‘check engine’ light

What’s behind that ‘check engine’ light on your vehicle’s dashboard. It could mean many different things. Check engine light is a one-light-fits-all icon.
What’s behind that ‘check engine’ light on your vehicle’s dashboard. It could mean many different things. Check engine light is a one-light-fits-all icon.

Brian Turner

It’s a pretty common scenario that plays out in auto repair shops of all stripes — a customer comes in with a check engine light (CEL) concern, a tech inspects their vehicle and prepares an estimate, but for any number of reasons, the client declines to complete that fix. It’s usually due to cost and, despite the annoying light, the vehicle may seem to operate reliably.

Officially, we think if your vehicle has an emission, safety, or critical system malfunction, you should have it repaired right away, or park it until you can have it addressed. In the real world, though, we know this isn’t always possible. In many of these un-repaired CEL cases, continued operation of your vehicle doesn’t present a big risk for a breakdown, save for contamination of the air we breathe. In fact, many in this boat simply think their one little vehicle doesn’t amount to all that much, in the grand scheme of things.

One CEL can mean many different things

One thing most drivers fail to realize is that the CEL is a one-light-fits-all icon. By ignoring the fault the vehicle brought to their attention, they may miss out on other more dire warnings to follow.

A good example is a CEL lighting up due to an evaporative emissions failure, caused by a malfunctioning leak detection pump. At first, this won’t affect the performance or reliability of most vehicles, but may cause excessive hydrocarbon emissions from the fuel system.

So, our Penny — you know, from Big Bang Theory, whose check engine light was constantly lit up — drives merrily along until sometime down the road, an oxygen sensor circuit fails and causes an excessively rich fuel condition, which permanently damages the catalytic converter. This can restrict exhaust flow leading to low power and high fuel consumption. Or, a crank position sensor starts acting up intermittently, and if it’s left to progress to total failure, it won’t let the engine start.

Get yourself a code reader

So, how can you avoid the “can’t see the forest (of hidden trouble codes) for the trees” syndrome? Simple: get yourself a simple automotive code reader, which can be purchased for as little as $50. Using one is as easy as plugging the reader into the diagnostic connector under the left side of your vehicle’s dash, and turning the ignition to the “run” position but not starting the engine.

Your detective work will only pay off if you know the code that triggered the CEL in the first place, though. If you plan on using this method, ask your tech to record it on your repair bill copy. If a new code pops up, you can easily decipher it with a quick search online.

How often should you run this test depends on the reliability of your vehicle, but since it only takes a few seconds, running it once or twice a month isn’t much of a chore. And while there are certainly more dire codes that will cause a CEL to flash rather than glow continuously, but the parameters for this aren’t universal, so it’s not something to count on.

Did this story inform or enhance your perspective on this subject?
1 being least likely, and 10 being most likely

Recent Stories