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Your Check Engine Light Is On – Now What?

Every modern car has a bevy of potential warning indicators but none as important as the Check Engine Light.

What is a Check Engine Light?

Dashboard warning lights
Dashboard warning lights

Most of us have already been in the situation where your check engine light comes on but even for those who haven’t experienced it, knowing what it is and how to deal with it is a vital skill. Your car is actually equipped with a number of sensors that can illuminate not just the check engine warning but they can also alert you to issues with other systems like your ABS braking components, an overheating engine, low oil pressure, and more. Of all the lights in the system, the ‘Check Engine’ warning is sometimes the toughest to understand and manage. So today, we’re breaking down exactly what that light is there for, what it can tell you as soon as it lights up, and how to determine exactly what turned it on.

What’s The Point of a Check Engine Light?

Check engine light
Check engine light

Many jokes have been made about the almost comically vague nature of the check engine light. That’s understandable since it can’t tell you anything specific without a specialized tool to find out what turned it on. Despite that, the light is still useful because it’s intended to let you know when a problem occurs. Importantly, most lights are set to turn on before major engine damage occurs so that whatever is wrong can be fixed. In addition, the light is most often illuminated by an issue with the systems that are directly tied to fuel economy, and with the price of fuel, nobody wants to spend more than they need to. Now, let’s talk about what to do when the light first comes on.

Why Does the Check Engine Light Turn On?

Car being towed
Car being towed

While the check engine light is pretty vague, it has two different modes when lit up, solid, and flashing. If you see the light come on and it simply stays there in total illumination then it’s likely that whatever issue turned it on isn’t in need of immediate attention. This is by far the most common type of check engine light. To be clear though, you don’t need to stop driving and pull over to call a tow truck. Still, you’d do well to figure out what turned the light on as soon as possible. Failure to determine the source as quickly as possible could result in additional damage.

If the light is blinking then it’s time to safely pull over if possible. Most of the time that the engine light is blinking there is a major issue that the onboard computer has recognized and severe damage to one or more systems is probable. Often, the car will actually lose some power and be noticeably slower. If your check engine light is flashing it’s best to get it to the side of the road safely and then have it towed to a local repair shop to avoid the risk of major engine failure or worse.

What Does a Flashing Check Engine Light Mean?

Open gas cap
Open gas cap

A solid check engine light can be caused by bigger problems like an intermittent misfire or smaller issues like a loose gas cap. It’s worth repeating though that most of the problems that turn the light on are directly related to fuel economy. When the light goes on, some engines are programmed to then send more fuel into the cylinder which has the effect of keeping engine temperatures a little lower and reducing the chance of engine damage due to misfires. If that happens it can really compound the potential fuel efficiency loss.

A flashing check engine almost always serves to indicate that the engine is experiencing a major issue like a consistent misfire, oil pressure loss, or worse. Continuing to drive a vehicle with a flashing check engine light will almost ensure that more damage will occur to the engine, the driveline, or the exhaust system to one degree or another.

What To Do When The Check Engine Light Comes On

Mechanic diagnosing car issues
Mechanic diagnosing car issues

The solution for each type of light is the same but the timeline is slightly different. As we’ve discussed, a flashing light demands quick action. In this case, getting it to a repair facility where they can properly diagnose the problem with a tool that reads exactly which system caused the light to come on.

Should the light be solid, it’s typically safe to continue your drive but it’s a good idea to take it to a shop as soon as possible to find out what’s wrong. Those who feel more mechanically inclined can also try taking the vehicle to an auto parts store where they’ll read the computer for you and give you an idea of where to start. Either way, you’re better equipped now to get that light sorted out and turned back off.

Editor’s Note: This post was originally published in November 2016 and has been completely revamped and updated for accuracy and comprehensiveness.

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Stephen Rivers

Stephen Rivers is a car enthusiast who loves all things built with passion, extending to nearly all car cultures. After obtaining an occupational studies degree in sports medicine, Stephen turned his attention to sports cars. He was employed as an auto shop manager, spent time in auto sales, and worked as a software developer for a racing company, but Stephen began writing about cars over 10 years ago. When he's not in front of a computer screen, he's racing his own Bugeye Subaru WRX in as many autocross and rallycross competitions as he can.

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