Home
Blog Car Care Advice 6 Reasons Why Your Check Engine Light Might Be On

6 Reasons Why Your Check Engine Light Might Be On

January 20, 2020

You’re driving along, minding your own business, when out of nowhere, a light pops up in your dashboard. It looks like the outline of a car’s engine, and the words “check” or “check engine” might appear next to it. It’s the check engine light – one of the most dreaded sights known to humankind.

If you find yourself in this situation, we have both good news and bad news. The good news is: The check engine light doesn’t always mean something is horribly wrong with your car. The bad news is: The check engine light can mean there’s something horribly wrong with your car. Don’t worry, we’ll explain.

Why Is My Check Engine Light On?

The check engine light can come on for many reasons. For example, something as simple as a loose gas cap can trigger the warning. And major problems, such as failed internal engine components, can turn on the light, as well. In order to really know what it is wrong with your car, it’s best to have a professional diagnose the issue.

What Could Cause the Check Engine Light to Turn On? 

There are countless reasons why the check engine light might pop on. This engine light is an important part of your vehicle’s on-board diagnostic system. Your car’s computer will illuminate the warning whenever it detects a problem with the powertrain (engine, transmission, and related components) that could increase tailpipe emissions.

For instance, a faulty gas cap, which would allow fuel vapors to escape into the atmosphere, can trigger the light. Likewise, an internal engine problem that causes a misfire, and therefore increased hydrocarbon emissions, can also turn on the light. And to make things more complicated, because each car is different, what triggers the light can vary by year, make, and model.

In other words: There’s no way to say exactly why your check engine light is illuminated without performing diagnostic work.

What we can tell you is that the check engine light comes on for powertrain-related problems. Issues with, say, your antilock braking system will trigger the ABS light, rather than the check engine light.

Of course, nowadays, because various parts of a vehicle are closely interrelated, in some rare cases, a problem within one subsystem (e.g., the antilock brakes) can trigger warnings in another subsystem (e.g., the powertrain). But for the most part, the check engine light means there’s a problem somewhere in the powertrain or related components. 

Solid vs. Flashing Check Engine Light Meaning

The check engine light meaning can vary depending on whether it is a solid or flashing light. 

Both a solid and flashing engine check light indicates that a problem has been detected. However, a flashing engine check light indicates that it is a serious problem that requires your immediate attention. If you see a flashing light, it’s best to contact a mechanic as soon as possible to prevent serious damage.

In some vehicles, the engine light will not flash when the situation is urgent. Instead, the light will appear in red or orange instead of yellow when an urgent issue has been detected.

The bottom line is you should always get your vehicle diagnosed and repaired regardless of whether the check engine light is solid or flashing. A flashing light conveys an urgent issue that needs to be taken care of right away. To protect your vehicle—and avoid costly repairs—seek a mechanic’s help as soon as possible.

Common Reasons Why Your Check Engine Light Might Be On

With that in mind, let’s explore some of the most common reasons why your check engine light might be on. 

1. Engine problems 

It goes without saying that engine problems can trigger the check engine light. A control module monitors engine operation via a collection of sensors. And when it detects a problem, it turns on the check engine light. 

2. Transmission problems

Your car’s transmission manipulates engine power and transfers it to the drive wheels. Because the two assemblies work together so closely, a problem with the transmission can also increase tailpipe emissions. Therefore, if the control module detects a problem with the transmission, it will turn on the check engine light.

3. Emissions equipment problems

Modern vehicles have a plethora of emissions equipment onboard. There’s the exhaust gas recirculation system, the catalytic converter, the evaporative emissions system – the list goes on and on. Each piece of the puzzle is designed to minimize tailpipe emissions, thereby, protecting the environment and making the world a safer place.

We won’t get into each of these components and systems individually because, frankly, there are too many to list. But trust us when we say an emissions equipment failure can easily turn on the check engine light. 

4. Modules and sensors (electronic powertrain controls) problems 

A wide range of sensors and modules govern today’s powertrains. What’s more, the modules communicate with one another over a vast data network. Issues with sensors, modules, networks and wiring can trigger the check engine light.

5. Air/fuel delivery problems

Your car’s engine needs the correct amount of both air and fuel to run properly. When it gets either too much or too little of one or the other, the control module will likely notice. The device then turns on the check engine light. 

6. Ignition system problems 

The ignition system includes the spark plugs, coil packs, and everything else needed to ignite the air/fuel mixture inside the engine. As you probably guessed, the control module monitors ignition system operation. And it will turn on the check engine light if it detects a problem.

Can Low Oil Cause the Check Engine Light to Come On?

Some people think that the check engine light indicates that their vehicle is running low on oil. The engine check light can turn on for a number of different reasons, but a low oil level is typically not one of them. 

Being low on oil is a serious problem, but it will not trigger your check engine light. It will, however, cause the oil light in your dashboard to turn on. This light looks like an oil can with a drop of oil dripping from its spout. If you see this light turn on, this could indicate that your vehicle needs more oil.

Is It Safe to Drive With The Check Engine Light On?

Pay close attention to your vehicle’s performance. Do you hear any strange sounds? Is it still driving smoothly or is it stopping and surging?

If you don’t notice anything unusual, it’s likely safe to continue driving your vehicle to a safe location, even though the check engine light is on. However, proceed with caution and be sure to get it diagnosed and repaired right away to prevent further damage.

If, however, something is off about your vehicle’s performance or if other dashboard lights suddenly turn on as well, it’s best to stop driving as soon as possible. Slow down and try to avoid quickly accelerating or shifting gears. Remain at this slow, steady pace until you can safely pull over and turn off your vehicle.

Engine Check Light Diagnosis: How A Mobile Mechanic Can Help

It can be hard to figure out what a check engine light means on your own, but a mobile mechanic has the tools and equipment to figure it out.

When the check engine light comes on, your car’s computer, which is often referred to as a control module, will store a corresponding diagnostic trouble code (DTC) in its memory. A professional mechanic can connect a scan tool or code reader to your vehicle’s OBD port, which is usually located in the steering column, in order to retrieve this diagnostic code. 

This code will not tell your mechanic the exact reason why your check engine light turned on. Instead, your mechanic will use the code as a starting point to perform further troubleshooting and to conduct additional diagnostic tests to determine the issue.

As an example, the diagnostic code P0300 is used to indicate that your engine is misfiring in more than one cylinder. It does not tell your mechanic which cylinders are affected by the problem or what is causing the engine to misfire in the first place. Thanks to this code, your mechanic will know where to start looking when investigating the reason the check engine light turned on.

Once the issue has been identified and repaired, the engine check light should automatically turn off. If it does not turn off or if it reappears, it may need additional repairs.

What to Do if Your Check Engine Light is on

You won’t know what the check engine light truly means until you have your car diagnosed by a professional. The warning could indicate something simple and harmless – or something serious that could cause further damage to your vehicle.

If your engine light turns on, you may want to try tightening the gas cap. Remember, a check engine light can turn on as a result of a loose gas cap, so firmly tightening the cap could solve the problem. If the light turns off, there’s no need to get your car serviced. If the light is still on, it could indicate a more serious problem with your vehicle.

You shouldn’t take any chances. If your check engine light is on, have a professional diagnose and repair the issue right away.