How To Reset The Check Engine Light On Mazda 3?

Were you driving one day, and the check engine light on your Mazda 3 suddenly lit up? And you’re not experiencing any problems with your car? We researched this question thoroughly to bring you an accurate answer and related information that you'd find useful.

Here are the simple steps you should follow to reset the check engine light on your Mazda 3:

  1. Turn off the ignition of your Mazda 3.
  2. Disconnect the negative terminal of your car’s battery.
  3. Wait for 15 to 30 minutes.
  4. Press the car horn intermittently while waiting for the 15-30 minutes to end.
  5. Reconnect the negative terminal.
  6. Start your Mazda 3.

Keep in mind, however, that Mazda does not recommend resetting the check engine light. If you think about it, doing so doesn’t really solve anything. To make things worse, resetting the check engine light could hide problems that can easily get worse in the long run.

Let’s look at the possible reasons why your Mazda’s check engine light is on, and then let’s talk about how to address these issues. Read on!

Interior if the compact hatchback Mazda 3, How To Reset The Check Engine Light On Mazda 3?

Why do I have a check engine light on my Mazda 3?

The check engine light is a way for your Mazda 3 to inform you that there are problems that affect its performance. Some are easy to address, while the rest will require professional help to fix.

Let’s go through the most common causes of a check engine light on your Mazda 3.

Engine check light on car dashboard.

Fuel cap is loose

Did you bring your Mazda 3 for a refill recently, and the check engine light went off shortly afterward? If this is the case, the most likely cause is a loose fuel cap.

The fuel cap or the gas cap creates a vacuum seal for your fuel tank. There is a sensor that detects if a vacuum seal has been achieved or not. Mazda 3 will alert you via the check engine light on your dashboard if it can't detect a vacuum seal on your fuel tank.

An improperly sealed fuel tank can be caused by several things. The gas cap could have a leak through a crack or hole. The sealing gasket on the gas cap could be missing, broken, or too worn out to be able to create a vacuum seal.

According to Capistrano Mazda, it is also possible that you are using the wrong fuel cap on your Mazda 3. This could happen if you’re using a pre-owned Mazda 3.

How to fix a loose fuel cap

The first thing you should do is loosen the fuel cap and then put it back in again. Make sure that the gas cap is screwed in tightly.

Replace the gas cap if there is a crack or leak. It also needs replacement if the gasket can no longer create a vacuum seal. If you’re using the wrong gas cap, you will have to replace it with one that is made for your Mazda 3.

Low fuel

The check engine light can also light up when your Mazda 3 is low on fuel. There should be a separate fuel gauge on the dashboard that gives you an estimate of the current fuel level. Check if your Mazda 3 is starting to get low on fuel.

If this is what’s causing the check engine light, then the only solution would be to take your Mazda 3 for a refill.

Make sure you put back the gas cap nice and tight after the refill so that the check engine light will not go on because of a loose gas cap issue.

Electrical problems

The check engine light will also warn you of electrical problems that can have an impact on your Mazda 3’s performance. Several electrical components directly affect your car’s performance.

Spark plugs

Used spark plugs

Spark plugs provide the needed electricity to ignite the compressed air and fuel mixture inside the combustion chamber. The pressure created by the combustion is what gives the engine the power to make your car move.

Thus, the check engine light will turn on if there is a possible problem with the spark plugs. But how can you be sure that it is the spark plug that triggered the check engine light?

If you follow your Mazda 3 maintenance schedule, then you’d know if your spark plugs are already due for replacement. Moreover, you can use the checklist of signs below that tells you to replace your spark plugs.

  • It is hard to start your Mazda 3
  • The engine misfires
  • Your Mazda 3 consumes more fuel than normal
  • Knocking or rattling noise while idle
  • Your Mazda 3 struggles to accelerate
  • Check engine light is on (of course)

Spark plugs can last between 20,000 to 30,000 miles. More expensive spark plugs made from noble metals can last up to 100,000 miles.

If the check engine light is on and you noticed one or more of the signs above, then it is likely time to replace your spark plugs.

Ignition coil

An ignition coil magnifies the voltage of your car battery into the thousands of volts needed that will allow the spark plugs to create a spark that will support an ignition. A bad ignition coil has similar symptoms with a bad spark plug.

Emission components

Your Mazda 3’s engine produces exhaust gases or flue gas because of combustion. It is the exhaust system's job to make sure these gases are released for the engine to function properly.

Thus, the check engine light will warn you if there is a problem with the components of the exhaust system, like the catalytic converter.

The catalytic converter

Your catalytic converter is responsible for neutralizing the hazardous byproducts of combustion—like carbon monoxide. As a result, it improves the fuel economy of your Mazda 3.

The catalytic converter was made to last the entire lifetime of your Mazda 3. However, putting off the repair for issues on other parts of your car can cause increased wear and breakdown on your catalytic converter.

In addition to the check engine light, these symptoms point to a failing catalytic converter:

  • Poor gas mileage
  • Decreased performance
  • Rattling noise

Replacing the catalytic converter can be very expensive. Have a professional check your catalytic converter or bring your Mazda 3 to a service center to check.

Cooling system

The cooling system is responsible for regulating the temperature of your Mazda 3’s engine, making sure that it doesn’t get too hot. The check engine light will warn you if there is a problem with the engine’s thermostat or if there is low or no coolant in your Mazda 3.

Coolant level

It is easy to check the coolant level on your Mazda 3. Just make sure that your engine is cool before you check the coolant level. The content of the coolant reservoir is under pressure, and opening it while the engine is hot can cause it to spray hot liquid that can cause injury.

The coolant reservoir of your Mazda 3 has markers that indicate the coolant level. If the coolant level is near or lower than the minimum level, do not use your Mazda 3 until you have added enough coolant to take the level to “F” or full.


Man holding used car thermostat, What Does a Car Thermostat Do?

The check engine light will also ignite when the engine thermostat is faulty. If the engine thermostat is faulty, the coolant inside your cooling system will not flow to cool your engine.

One way to test this is to wait until your engine is cool. Then turn on the ignition and leave your Mazda 3 on idle. The hose going back to the radiator should start to become warm the longer your engine runs. This means that the thermostat is working.

If the hose going back to your radiator remains cool, this means that the thermostat is no longer functioning. The thermostat should open to let the warm coolant flow into the radiator to be cooled.

On the other hand, if the thermostat is stuck in the open position, the engine will not be able to achieve the required operating temperature.

The video below shows you how to replace the thermostat.

Just remember that the coolant is a highly toxic liquid. Make sure that you or the surface of your car doesn’t come in contact with it. Bring it to your recycling center once you’re done.

If you're in the market for a replacement thermostat, a Mazda replacement thermostat is available aftermarket. See it on Amazon.

Mass airflow sensor

The mass airflow sensor monitors the flow of air into the engine. The combustion inside of your Mazda 3 requires a specific amount of air. Thus, a problem with the airflow will trigger the check engine light warning.

How to be sure that the mass airflow sensor is at fault?

Check out the list of signs that the mass airflow sensor needs to be replaced below:

  • Acceleration problems
  • Black exhaust
  • Difficult to start the engine
  • Bad fuel efficiency
  • The engine hesitates and/or surges

The video below shows how to clean the mass airflow sensor. If you need to replace the mass airflow sensor, follow the same video, but put in a new mass airflow sensor instead of the old one back into your Mazda 3.

If you need to replace your mass airflow sensor, the OEM mass airflow meter/sensor for Mazda 3 is compatible. See it on Amazon.


Mazda 3 Hatchback in front of a traditional windmill

Resetting the check engine light on your Mazda 3 can conceal issues that can get worse if left unrepaired. Any problem that triggers the check engine light should be resolved first before resetting it.

Here are a couple of articles about check engine light that you might be interested in.

Can Hot Or Cold Weather Cause The Check Engine Light To Come On?

Can I Drive a Car with the Check Engine Light On?

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