Check Engine Light On and Off Intermittently [Causes and Fixes]

When the check engine light comes on, you should take your car to a mechanic to get it checked. But what if the check engine light turns on and off intermittently? What causes this, and how to fix it?

There are several possible reasons why a vehicle’s “check engine” light turns on and off intermittently. The possible causes for this are a loose gas cap, a faulty oxygen sensor, bad spark plugs, or a faulty mass airflow sensor.

The check engine light turns on and then off because the main computer might not be correctly registering the problems at all times. So, when you encounter this issue, it’s always best to have your vehicle checked by a professional mechanic.

Read on to learn more about why the check engine light turns on and off intermittently. We will also talk about what you should do when you encounter this issue.

Check Engine Light On and Off

check engine light on and off

Possible causes of the “check engine” light coming off and on are:

  • A loose gas cap
  • A faulty oxygen sensor
  • Bad spark plugs
  • A faulty mass airflow sensor

A check engine light that turns on and off intermittently is not uncommon. If the check engine light turns on and then off, it is possible that the main computer is not correctly registering the problems at all times. So, when you encounter this issue, it’s always best to have your vehicle checked by a professional mechanic.

Experiencing this and not knowing what’s wrong with your car is quite frustrating. That’s why it’s best to learn more about the different reasons why this happens. This article will discuss everything you need to know about a check engine light that intermittently turns on and off.

But, it’s important to understand first what a check engine light is.

What Is the Check Engine Light?

The Check Engine Light is also popular as the malfunction indicator lamp. When your vehicle encounters a problem, you’ll notice a yellow or orange light appearing on the dashboard shaped like an engine. In most cases, the word “CHECK” or the words “CHECK ENGINE” appears too, and it’s quite impossible not to notice it.

It’s true that once the check engine light turns on, there must be something wrong with your car. But, contrary to popular belief, it doesn’t always mean that your car has a serious issue. So, there’s no need to panic when this happens to you, especially if you’re in the middle of the road.

As soon as you notice the light turning on and off intermittently, it doesn’t mean that your car engine will just suddenly shut off. It only alerts you that there’s an issue that has to be fixed soon. So, find time to bring your car to a car care shop as soon as you can. Don’t ignore the warning sign.

What Causes the Check Engine Light to Turn on and off Intermittently?

check engine light on and off intermittently

There are several reasons why the check engine light turns on and then off. Among these are the following:

  1. Loose Gas Cap
  2. Faulty Oxygen Sensor
  3. Bad Spark Plugs
  4. Faulty Mass Airflow Sensor

Let’s delve into each of these items and see how you can fix them:

1. Loose Gas Cap

As earlier mentioned, a check engine light that goes off doesn’t always mean a serious issue with your car. It can be as simple as having a loose gas cap. If your car’s gas cap is not tightly closed, it could cause the light to come on and off. The light will only permanently disappear once you tighten the gas cap.

This is one of the simplest, if not the simplest, issues you encounter with the check engine light. So, it’s important to make it a habit to check and ensure that the gas cap is properly closed.

2. Faulty Oxygen Sensor

The oxygen sensor in your vehicle ensures that your engine receives the correct amount of oxygen consistently. The oxygen mixes with the gasoline to keep the engine going. The combustion process will not normally work if there is an inadequate amount of oxygen.

At the same time, too much oxygen is a disadvantage too. It can cause damage to the car engine. Suffice it to say that there should be a balanced mix of oxygen and gasoline to keep the engine going. The job of the oxygen sensor is to detect this.

Oxygen has an important role in your car’s engine. That’s why an insufficient oxygen supply can cause the check engine light to turn on. If you don’t get this fixed, the light will most likely turn on and off over time. Worse, if the light permanently turns on, it can mean that it has already caused serious damage to your engine.

If you encounter this issue, it doesn’t mean that it’s as simple as having a loose gas cap. A faulty oxygen sensor is something more serious than that. It’s best to visit a car care shop as soon as possible so that the issue can be dealt with accordingly.

3. Bad Spark Plugs

Spark plugs that have gone bad have several indicators. One indicator is if your car doesn’t start as efficiently as before. Another indicator is if it doesn’t accelerate the way it used to. 

If the spark plugs are worn out, it can impact the engine’s combustion process. Once the main computer detects this, the check engine light will most likely turn on and off.

When your car’s spark plugs start to wear out, you will still be able to drive your car. However, it can eventually cause severe damage to your car if you don’t address the problem.

Your car’s check engine light that intermittently goes on and off should serve as a warning. It should not cause any panic. But it should not be ignored as well.

4. Faulty Mass Airflow Sensor

If you didn’t know, the natural air coming from the outside passes through the vehicle’s air filter. It then makes its way to the engine. Your car has a mass airflow sensor to measure the amount of air getting into the engine.

The mass airflow sensor detects if the air reaching the engine is too much or insufficient. If the amount of air is not right, it can result in reduced fuel economy. You will be alerted through your car’s check engine light.

This issue is not to be ignored. A faulty mass airflow can affect other parts of your vehicle. These include the oxygen sensor, the spark plugs, and even the catalytic converter, among others.

Can You Ignore a Check Engine Light That Turns on and off Intermittently?

An on-and-off check engine light doesn’t mean that your car is in better shape than a car with a light that is constantly on. Either way, it both means that there is an issue that needs to be dealt with.

If the light is not constantly on, it can mean that the issue is simple and can easily be fixed. However, it can also mean that your car’s main computer doesn’t get to register the issue at all times.

While it should not cause you any panic, it should not cause you to relax too. Don’t ignore an on-and-off check engine light. Instead, bring your car to your trusted car care shop so you can identify and address the issue immediately.

Check Engine Light On and Off Intermittently FAQs

check engine light blinks

Why the Check Engine Light Turns On

Let’s also talk about the reasons why a car’s check engine light constantly turns on. It’s best to know this too. Again, if the car’s main computer doesn’t detect the issue at all times, it can result in an on-and-off check engine light too.

A light that is constantly turned on most likely has issues on the following:

  • Evaporative emissions purge solenoid
  • Thermostat
  • Evaporative emissions purge control valve
  • Fuel injectors
  • Ignition coils

These issues do not cause the check engine light to go on and off in most cases intermittently. Instead, they will most likely cause the light always to stay on. It will continuously stay on until you have finally addressed the issue.

What Should You Do When You Encounter Check Engine Light Issues?

Unfortunately, some drivers ignore their cars’ check engine light. This is because they can still use their cars even if they know there are issues.

While you choose to do the same, it is not a good practice to do so. The check engine light is not there to be ignored. It should serve as a warning, and you have to do something about it.

Bringing your car to a car care shop is the right thing to do. Only a professional mechanic can efficiently detect the exact issue of your car. They have a special tool that can interpret the codes indicated in your car’s main computer.

You indeed have to spend money on car repairs. But if you don’t address it immediately, your car’s issues will pile up. Car repairs will eventually be more costly. Worse, you might not be able to bring back the good ol’ condition of your car.

Will You Be Able to Sell a Vehicle with a Check Engine Light That Goes on and Off?

Can you still sell your car with a check engine light that intermittently goes on and off? The answer is yes. But you might have a difficult time doing so.

In most cases, those who will be interested are people who are into buying and selling cars. They can buy your car and have it fixed before offering it to potential buyers. However, you might not be able to sell it at a good price.

If you’re looking into selling it to a private buyer, it is possible too. But then again, expect the potential buyers to ask for a big discount. You can’t deny the fact that you are still offering them a car with existing issues.

It’s a challenge to sell a car with issues. If you want to sell it faster, you have to fix the issues first. That way, you can also sell it at a good price.

What to Do with a Check Engine Light That Goes on and off While Driving?

If the check engine light turns on and off while driving, you should not panic. However, make sure to keep your presence of mind.

First, check the dashboard gauges and lights. Determine if there’s a low oil pressure warning. Also, check if the engine is overheating. If any of these issues arise, you are recommended to pull over as soon as you can safely.

Also, if you notice changes in engine performance, it is best to reduce speed. Make necessary adjustments according to the demands of your engine.

Conclusion – Check Engine Light On and Off Intermittently

There are several reasons why a car’s check engine light turns on and off intermittently. It most likely has a loose gas cap, a faulty oxygen sensor, bad spark plugs, or a faulty mass airflow sensor, among others.

The check engine light turns on and then off because the main computer might not be correctly registering the problems at all times. So, when you encounter this issue, it’s always best to have your vehicle checked by a professional mechanic.

Car issues that cause the check engine light to turn on and off can range from simple to severe. Since you can’t identify this outright, it is always best to have a professional mechanic check your car. Nobody else can determine this efficiently but them.

Again, the check engine light is a car feature that serves as a warning that something in your car has to be fixed. Your car can indeed continue to serve its purpose even with issues. But this is only short-term.

If you ignore the warning that your check engine light provides, it can lead to severe damage to your car. The bottom line is, once you notice the light on, don’t ignore it. If you want your car to serve you for a long time, take good care of it.