Demystifying the Cause of the “Check Emission System” Message in Honda Cars

Vehicle emission systems in recent years have become more sophisticated to ensure fewer pollutants are entering the environment. This also includes car brands such as Honda. Over the years, the company has upgraded its emission system to ensure its various models meet strict emission standards. That is why you may be worried when you get the message “check emission system” in Honda.

Seeing the message “Check Emission System” in Honda means there can be a problem with the vehicle’s emission system. This happens because of a faulty oxygen sensor, a dirty air filter, an exhaust leak, a loose gas cap, and more, as we will see later in the guide.

We look keenly at the emission systems in Honda vehicles, their components, what can cause the error, and how best to resolve the message and keep the car running smoothly.

Role Of Emission Systems In Vehicles

Each vehicle brand, including Honda, must have proper emissions systems. The work of an emission system is to minimize the number of harmful pollutants leaving the car and entering the environment.

The emissions systems are part of the vehicle’s engine and exhaust system. They are in the middle of these two systems. Once the exhaust gases come from the engine, they are passed through the emission system to remove the pollutants.

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Besides reducing harmful substances such as carbon monoxide, nitrogen oxides, hydrocarbons, and particulate matter, the same system is also vital for optimizing fuel efficiency.

Below is a quick video showing how the emission systems work in vehicles.

YouTube video

Emission Control Components in Honda Vehicles

As a brand, Honda has several emission control components that help it meet regulatory requirements. These components are;

  • Catalytic converter:A catalytic converter contains catalysts vital for converting harmful exhaust gases into being less harmful through chemical reactions. The catalytic converter reduces hydrocarbons, carbon monoxide, and nitric oxides.
  • Oxygen sensors:As the name suggests, the oxygen sensor monitors the oxygen levels in the exhaust gases and provides feedback to the ECU. This information helps the ECU know how to adjust the air-to-fuel ratio to achieve optimal combustion efficiency. The result is better fuel economy.
  • Exhaust Gas Recirculation (EGR) valve: This valve recirculates part of the exhaust gases into the combustion chamber. This should lower the peak combustion temperature and the formation of NOx emissions.
  • Evaporative Emission Control (EVAP) system: This system in the Honda emission system prevents the release of fuel vapors into the environment. It captures and stores the fuel vapors in a canister until they can be routed back into the engine for burning.

At this point, you can easily see why such a system should always be working correctly.

What Does the”Check Emission System” Message Mean

The moment you see the “Check Emission System,” just know there is a problem with the emissions system in your Honda vehicle. Sometimes people tend to ignore this message and end up experiencing more issues with the vehicle down the line.

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So, run an OBD-II scan to ascertain the issue with your Honda vehicle. Some things that can trigger this message include faulty oxygen sensors, catalytic converter issues, malfunctioning fuel injectors, EVAP system malfunction, a loose gas cap, and others.

Cause of Check Emission System Message in Honda

Cause of Check Emission System Message in Honda

Knowing what could be the cause helps know the best remedies. Below we look at what could lead to the message “Check Emission System” in Honda vehicles.

Faulty Oxygen Sensors

We have already discussed the importance of oxygen sensors. Now you can imagine if they are not working, there will be no feedback to the ECU on how it should adjust the air-to-fuel mixture in the combustion chamber. This imbalance triggers the message “Check Emission System” in Honda.

Catalytic Converter Issues

The catalytic converter failing means that the harmful emissions are not reduced to the recommended levels. When this happens, the emission systems message appears on the dashboard to alert the driver.

It is common for catalytic converters to develop issues after a couple of years. It is mostly because of age, but engine misfires, contaminations, and other factors can lead to a damaged catalytic converter.

Another reason to know it is the catalytic converter having issues is when there is reduced engine performance. Expect to hear rattling noises from the converter and smell sulfur from the exhaust.

Malfunctioning Injectors

Fuel injectors always need to work correctly so that you have a precise amount of fuel in the engine cylinders.

The injectors malfunctioning means there is no proper ratio of fuel and air in the combustion chamber. This leads to poor combustion and increased emissions. So, you can still check the injectors when you see the check emission system message.

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EVAP System Problems

The EVAP system is still as important as the catalytic converter in capturing the fuel vapors to prevent them from entering the atmosphere. When there are issues with the system, expect the message check emission system to appear.

Also, having a loose gas cap means the fuel vapors are escaping, thus resulting in the same fault.

The other potential reasons you may see the emission system message are because of the;

  • Misfires
  • Airflow sensors
  • Vacuum leaks
  • Other sensor malfunctions

Resolving The Check Emission System Message in Honda

Since most reasons for the “Check Emission System” message are technical, it is best to use a certified Honda technician to solve the problem.

A technician will have the right tools and expertise for diagnosing and repairing of the broken parts in the emission system.

However, if you can do it yourself, then go for it.

Remember, most of these parts will simply need replacing rather than repairing. A good example is the faulty oxygen sensor. We recommend replacing it with a functioning one to get accurate readings.

A catalytic converter can sometimes be repaired, depending on the damage extent. However, if the damage is extensive, you are better off replacing it.


How long can you drive with the Check Emission System message?

Once the warning comes onto your dashboard, it is best to have the car checked as soon as possible. Do not wait for days or weeks before addressing it. Sometimes it can be a simple fix.

How can you reset or clear the check emission system message in Honda?

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Some people opt to turn off the engine and disconnect their battery for a minute or two. However, the best method is to use an OBD-II scanner to find out what the issue is, and once it is addressed, use the same tool to clear the code.

Why is it important to address the check emission system in Honda promptly?

The light comes on when there is a problem with the emission system. This is enough to tell you why it is important to address it. The vehicle’s performance may deteriorate with time, and there is an environmental impact if the vehicle does not meet emission standards.


The emission system in Honda serves an important role in monitoring the performance of various system components and alerting you when there is an issue. People might not take this seriously, such as a check engine light, but it is still important.

An example is when the oxygen sensor is not working well, you end up losing fuel efficiency. As such, get the vehicle to a specialist for repairs where necessary and keep it from showing the check emission system message.