Why Is My Check Engine Light On? (7 Possible Reasons)

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Why is my check engine light on? There are a lot of issues that can trigger the check engine light to illuminate on your car’s dashboard. When this light comes on, it is advisable that you find a safe spot to pull over and check your engine for possible faulty components.

The most common issues that illuminate the check engine light include clogged filters, faulty sensors, and leaky hoses. For example, if your head gasket is leaking, the check engine light may illuminate.

In this article, we’d explore the various possible scenarios that can cause the check engine light to come on, and how you can fix them.

What Does The Check Engine Light Indicate?

Just as it reads, “Check Engine,” when the icon illuminates on your dashboard, it means you should go check your engine.

Modern cars are built to feature a centralized computer system that can quickly detect faulty components and display a corresponding sign/icon on your dashboard.

While there are many other icons on a typical car dashboard, the check engine icon/light is what mostly gets activated whenever the car computer detects an issue. Well, it’s nothing to panic, most times the detected issue is something you can fix yourself.

Read Also: Why Oil Pressure Light Comes On And Off

Why Is My Check Engine Light On?

Why Is My Check Engine Light On

As said earlier, the reason why the icon got illuminated could be vast; it could be that you’ve got a bad catalytic converter, a failing oxygen sensor, faulty fuel injectors, and many other possible issues.

1. Problematic Emissions/Exhaust System

The exhaust and emission systems are the same. Typically, this system comprises a catalytic converter, a muffler, a resomer, and the tailpipe.

If any of these components should get clogged or incur physical damage, it can trigger the check engine notification to come on.

That said, when the notification comes on, one of the first places to check is your exhaust system. If you check and everything looks good there, move on to the next systems that could cause the problem.

2. Faulty/Bad Sensors

From wheel speed sensors to oxygen sensors, when one or more sensors are no longer sending required signals to the central computer, it can activate the check engine notification. The oxygen sensor detects the amount of unburned gas in the exhaust system.

Wheel speed sensors transmit your tire rotation speed to the central computer. The number of wheel speed sensors on a vehicle depends on the number of wheels the vehicle has. If one of the sensors goes bad, the check engine light may appear.

Read Also: How Does a Wheel Speed Sensor Work?

3. Modules and Wires

Apparently, modern cars are built with pretty many modules, and of course, there are lots of wired connections.

If any of the modules or wiring goes bad, it can trigger the check engine light. The modules and wiring are as sensitive as the sensors.

4. Transmission Problems

Now we’re at the main possible cause. When one or more components that make up your vehicle’s transmission system are faulty, apparently, the check engine icon would illuminate. But, what are the components that make up the transmission system?

The transmission system comprises the gearbox, clutches, and even brakes. These are all very crucial; thus, if any of them should go bad, or show signs of failure, it calls for urgent intervention and repair/replacement.

5. Faulty Internal Engine Components

The engine doesn’t just function on its own, there are several internal moving parts that push the engine to work.

If peradventure one of those moving parts stops moving, it could cause overheating, and also trigger the illumination of the check engine notification.

Read Also: Symptoms Of A Bad Speed Sensor

6. Clogged Filters

If you have a bad or clogged oil/fuel filter, it would restrict oil and diesel flow into the engine; thus, your engine would not perform as supposed and that’s enough to turn on the notification on your dashboard.

7. Other Possible Issues

Other possible things that can cause the check engine light to come on include a faulty gas cap (head gasket), spark plugs, fuel injectors, and carburetors. Furthermore, faulty coils can also cause the light to appear.

What To Do When Check Engine Light Comes On?

While your car can drive with the check engine light still on, it is advisable that you stop driving when the light comes on and check what actually triggered its illumination.

You can check physically for physical damages or use an OBD-II scanner to troubleshoot further when you can’t find physical damage.

So, once the light appears, find a safe place to park your car and start the troubleshooting or physical checks. If you can’t find anything, drive to a mechanic workshop and have a professional auto mechanic check the car.


After the check or troubleshooting, ensure to fix or replace whatever made the check engine light appear.

If the issue is with your spark plugs or injectors, those components are not too expensive to replace.

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