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The Right Way to Handle a Check Engine Light

We’ve all seen it before: the ominous amber-colored glow of the “Check Engine” light, or its close relative, the “Service Engine Soon” light. Most of us probably see that and think something like, “oh great, how much is this going to cost me?” But before you ask that, there are some other fundamental questions that a DIY-er should ask to better understand the situation.

What makes the light come on in the first place?

Modern cars have many, many sensors all throughout the various systems, mostly to monitor tailpipe emissions. When the car’s computer detects anything abnormal from one of these sensors, the check engine light comes on.

What does it mean?

Of course, this is the million-dollar question. It can mean any number of things, based on which sensor’s code has caused the computer to record a problem. It could be as simple as a loose fuel filler cap, or as complicated as a major engine problem.

When the light comes on, it’s because the computer sees that one of the sensors has raised a red flag, so to speak. Generally this red flag either means that the sensor has found a problem, or that the sensor is the problem and needs to be replaced.

What should I do?

As soon as you can, take your car to get checked out. The computer will need to be read by a scanner that can communicate with it and retrieve the stored codes. Auto parts chain stores will often offer this code-reading service for free. From there, a mechanic has a good starting point for a diagnosis of what repairs or procedures will be needed. With luck, it may be something you can handle on your own, saving a significant chunk of change. If so, that should end up lessening your anxiety next time that light pops up.

What should I not do?

Number one, don’t ignore it. Like the rest of us, you’re very busy, and you’re thinking that since your car still starts and drives fine, you should be good, right? While this is certainly possible, it’s far from a sure thing, and the car could just as easily have a serious problem as a trivial one. So, resist the temptation to put a black piece of tape over the light and go along your merry way.

Number two, if you should happen to get the code or codes read at an auto parts chain, don’t assume that the corresponding sensor is always the problem and that replacement is always the answer. The chain stores check your codes for free, because they hope you will buy a part to try to make the check-engine light go away. The parts stores may not be intentionally deceptive, but many people have needlessly purchased and installed new parts (based on the diagnostic code) when they were working just fine all along, and the root problem was elsewhere.The moral of the story: a guess will almost always cost more in the end than a professional diagnosis.