Why Is My Check Engine Light Flashing? (10 Reasons Why)

If you have a car, you know your dashboard has several icons that light up to signal that your car needs something. However, one somewhat vague yet alarming icon to watch out for is a flashing check engine light.

If you noticed your check engine light flashing, you probably want to know why. We did the research, and here is what we learned about the matter!

Why Is My Check Engine Light Flashing?

1. An Issue With Your Sensors

A common reason your check engine light is flashing is that you have an issue with your cars sensors.

For instance, the mass airflow sensor will measure the amount of oxygen that goes into your cars engine to ensure enough oxygen is combined with the fuel.

Another example is the oxygen sensor, which checks how much unburned oxygen is in the cars exhaust.

As such, these sensors are in charge of measuring the air in your engine and sending the information to your cars computer to create any necessary adjustments.

Therefore, if any of these sensors are failing, they will send the wrong information to your cars computer, leading to various imbalances that can make your check engine light flash.

2. Bad Spark Plug

A spark plug is an important part of your car that helps ignite the mixture of fuel and air within your cars combustion chamber to create power.

However, a faulty spark plug will not create the spark needed to ignite the fuel and air, meaning your engine will not start while your check engine light flashes.

Read More:  Why Won't My Garage Door Open? (11 Reasons Why)

Usually, you would have to have your spark plugs replaced since you cannot repair a spark plug.

3. Damaged Ignition Coil

While your spark plug helps your engine start, an ignition coil is another important part of your engine that helps your spark plug work.

Generally, high voltages are sent by the ignition coil to the spark plug to allow the spark plug to ignite the air and fuel within your cars combustion chamber.

With that, your ignition coil will send little to no volts to your spark plug if it is faulty, causing your car to misfire and trigger your check engine light.

4. Faulty Battery And Charging System

A dead battery is another common reason your check engine light would appear since your car needs a battery to run.

Usually, you can have your battery recharged; unless the battery is damaged and old, then you would have to replace the battery.

Additionally, there could be an issue with your charging system that causes your check engine light to flash, not your battery.

For instance, the alternator that turns mechanical energy to electrical energy could malfunction, making your check engine light illuminate.

5. Bad Fuel Injectors

Bad Fuel Injectors

Most gas-powered cars, especially ones that run on diesel, will have fuel injectors for the engine’s cylinders.

That said, the fuel injector’s main purpose is to control how much fuel is sprayed during the cars intake cycles.

However, the fuel that passes through these fuel injectors can contain impurities that will eventually clog the fuel injectors.

Read More:  Why SUVs Are Better Than Cars? (9 Reasons Why)

Plus, some of these impurities can damage the fuel injectors, creating gashes or holes.

So, if your fuel injectors have gone bad, there won’t be enough fuel moving throughout your cars engine, making your check engine light flash.

6. Bad Gas Cap

All cars that run on gas will have a fuel filler cap or gas cap that keeps the fuel tank free of dirt, debris, and dust.

With that, a common reason why your gas cap can trigger your check engine light is that you did not put the gas cap on properly after you refueled your tank.

Further, this is because the gas cap has a vacuum seal to shut the fuel tank tightly, but you can just put the gas cap on properly to fix this issue.

However, the vacuum seal in the gas cap can get old or break, so you would have to replace your gas cap.

7. Your Engine Is Too Hot

If your engine is too hot, your engine will overheat, which can be very dangerous and cause your check engine light to flash.

For instance, your valves, sensors, etc., can get damaged from a hot engine since the heat can make the fuel spontaneously detonate.

Usually, you will know that your engine is too hot if smoke seeps out of the hood of your car or your temperature gauge is running high.

8. Water Leaking Into Engine Parts

Occasionally, the issue may not be the engine itself but external elements that are causing your check engine light to flash.

Read More:  Why Is Toyota Venza Discontinued? (9 Reasons Why)

For example, rainwater can seep through your engine and hit the electrical components of your car, making your check engine light illuminate.

9. Leaking Vacuum Hose

Another common reason your cars check engine light flashes is that you have a leaking vacuum hose.

That said, your car contains various vacuum hoses that can get old, causing the vacuum hoses to crack and make a leak.

10. Faulty Catalytic Converter

Since your catalytic converter is an important part of your engine, a failing catalytic converter will make your check engine light flash.

Typically, you can tell if you have a faulty catalytic converter if your car has a rotten egg smell.

To know more, you can also read our posts on why your check engine light is on Volkswagen, why your check engine light is flashing and car is shaking, and why your engine is shaking.


Usually, a check engine light will flash because there is a problem with the engine, but pinpointing the exact cause can be difficult.

That said, there are common reasons why a check engine light flashes, including a damaged or loose gas cap, damaged sensors, and more.

Leave a Comment