Check Emission System: A Thorough Guide To Warning Lights

Check emission system warning light usually confuses many people. What does it mean, why does it turn on, and how do you fix it?

Check Emission System

These questions probably pop up in your mind as well, especially if it’s your first time owning a vehicle.

In this article, you’ll learn all about this warning light and more!

What Is Meant by Check Emission System?

The check emission system (also known as check engine light) is a warning light indicator in your dashboard that indicates any fault or issue in the vehicle’s emission system. This car reduces harmful substances entering the atmosphere. When any problems appear in the system, the warning light goes on.

Usually, the gasses this system reduces include carbon monoxide, hydrocarbons, nitrogen oxides, and other pollutants the engine produces during combustion. So, if any issue in this system damages the atmosphere on the one hand, it can also adversely affect your vehicle’s components.

– Fixing or Resetting the Emission Warning Light

Although the safest, most recommended, and best way to fix or reset check emission system light is by fixing the problem rather than manually resetting it, you can still do so. One method is by disconnecting the battery for 5-10 minutes.

Turn on the ignition switch during disconnection, press the pedals, and turn on the headlights or horn to drain any remaining electricity in the system. After that, reconnect the battery. It will reset all electrical components, along with the warning light.

– Cost of Fixing the Check Emission System Light

Usually, the cost of fixing a check emission light depends on the nature of the problem. Its labor cost can range from a mere $50 for minor issues, like loose gas caps or faulty oxygen sensors, to above $200 for significant issues, like replacing a mass airflow sensor or ignition coil.

Cost of Fixing the Check Emission System Light

On the other hand, more serious issues that involve replacing parts such as converters or plugs are likely to cost much more due to higher labor costs and expensive replacement parts. For instance, replacing a failed catalytic converter may set you back anywhere from $500 to $2,000, depending on the make and model of your car.

– Ignoring the Check Emission System Warning Light

Do not ignore the check emission system warning light, as ignoring a check engine light can have serious consequences for your vehicle. Since this warning sign alerts you to potential issues with your vehicle’s emissions system, you can’t leave it as it is.

It informs you about problems like faulty systems, components, or side issues with exhaust gas recirculation, which are vital for a healthy vehicle’s life. So take immediate action when the check engine light appears on the dashboard.

The best practice will be checking your car with a qualified expert who can thoroughly diagnose your vehicle. This will ensure any necessary repairs are made promptly and prevent small problems from becoming bigger ones in the future. Otherwise, if you ignore the warning light, you risk further damage, and it will be more difficult (and more expensive) to diagnose and fix later.

– Preventing the Emission System Light From Turning On

You can prevent the emission system light turning on through regular maintenance. Service your car engine every two years for efficient performance. Also, perform regular maintenance of filters and other components to keep them clean from dirt and debris. Regularly schedule tune-ups to identify any problem or issue before it gets worse.

When you observe any worn-out component, replace it immediately. You can also prevent the emission light from turning on by checking fluid levels like oil or coolants. Moreover, go through the vehicle’s manuals to perform repairs or other maintenance in a timely manner. You should also regularly check the fuel injection system and look for any contamination.

Lastly, it is always important to choose a high-grade or recommended gasoline for your vehicle. Selecting a poor-quality gas will degrade the emission system, produce toxic gasses, and cause the warning light to come on more often.

Besides these necessary precautions, you can also check hoses, belts, or pipes for damage. Otherwise, it will be best to regularly take your vehicle to a trusted repair shop for inspections (whether you need it or not). It will ensure problem detection even if you don’t suspect it.

Why Does the Check Emission System Light Go On?

The check emission system light can turn on due to multiple reasons. It can be due to a faulty emission system, air filter, or ignition system. It can also be due to faults in the particulate filter or in the mass airflow.

Why Does the Check Emission System Light Go On

These common causes are mentioned below.

– Fault in Your Emission System

If your emission system is faulty and produces too much carbon monoxide, the emissions light may go on. The oxygen sensor of emissions controls the level of oxygen burning in the engine.

If the engine consumes too much or too little oxygen, it will produce CO or other harmful gasses, so the light may turn on due to a bad oxygen sensor.

– Fault in Mass Airflow

The mass airflow sensor in the engine determines how much air will enter the fuel into the combustion chamber. In case of a faulty mass airflow, the engine won’t get the right air-to-fuel mixture, which turns on the check engine light.

The engine will have a bad ratio, which will either consume too much air or an extra fuel-rich mixture. In the end, it can harm your vehicle’s components.

– Fault in the Particulate Filter

A dirty air filter in the exhaust pipe may also trigger this indicator. When the exhausting air leaves the engine, it passes through the particulate filter that eliminates harmful and toxic substances.

So when the system detects a contaminated gas through a faulty air cleaner, it will show you the check emissions sign.

– Fault in the Ignition System

The ignition system controls the spark that ignites the air-fuel mixture in an internal combustion engine. It usually consists of many vital components, including spark plugs, glow plugs, distributor caps, rotors, coil packs, and wires.

So, when this system malfunctions, it can trigger your vehicle’s emissions control light. Hence, the engine light may turn on.

– Fault in Positive Crankcase Ventilation

This emission problem is most common in the Honda Civic and Odyssey vehicles. These ventilation systems in Honda consist of hoses and are responsible for removing unwanted gasses from the engine’s crankcase.

But when these hoses are damaged or clogged, they don’t do their job effectively, causing the check emission system in Honda Civic and Odyssey to turn on.

– Fault in Evaporative Emissions Control System

The evaporative emissions control system has many canisters, hoses, and fittings to filter dangerous vapors. The EVAP system is also found primarily in Honda cars.

If there’s a fault in the emission control system, it automatically causes the check emission system in Honda Odyssey and Civic to turn on.

What Are Different Check Emission System Light Scenarios?

The different check emission system light scenarios include the light remaining on or flickering. Sometimes it lights up only in particular cases, while at other times you will be able to observe a significant change in your vehicle’s performance as soon as it turns on.

What Are Different Check Emission System Light Scenarios

In any situation, you cannot ignore the warning light.

– Warning Light Turns on or Flickers in Special Conditions

You might observe this warning light coming on under special conditions, like going on a specific route or tuning into particular car system settings. The condition may be triggering a fault in the car’s emission system.

Warning Light Turns on and Flickers Continuously

If it turns on for a while in a specific scenario, the problem will likely be minor or false. But you can’t ignore it as you are unsure about the severity, so it is better to pause the work and make a quick stop at the nearest repair shop.

– Warning Light Turns and Stays On

If the check engine light turns on continuously and doesn’t even flicker, but you don’t observe any performance changes, the problem is perhaps in the control system. Usually, it happens when there’s a fault in the spark plugs, or the oxygen sensor is taking incorrect readings.

However, although you don’t notice any performance difference, it is not safe to continue driving. Take your car to a trusted technician as soon as possible. But if you are in a hurry, stop at a nearby repair shop for quick advice. It will be best if you postpone the drive until you service your car.

– Warning Light Turns on and Flickers Continuously

If the light doesn’t only come on but also flickers rapidly (like twice or more per second), take immediate steps. It signals a severe condition. It means the catalytic converter is damaged, extremely hot, or the worst case scenario, at the brink of catching fire.

It is important not to mistake this rapid flicker for slow flashes (mentioned in the first scenario). When it happens, pull over immediately and call an expert. It is advised not to drive the vehicle anymore, even if everything cooled down after some time and looks normal. Wait for the automotive towing truck to rescue your car.

– Warning Light Turns on and You Observe a Performance Difference

As mentioned earlier, it is not so problematic if the light turns on but you don’t observe any performance changes. However, when you observe a change after the warning sign is on, again stop the car immediately. It indicates a fault or failure of a vital component or system.

The car will automatically stop, stall if you don’t, or raise any other severe issue, so it’s better to pull over before the problem elevates and call the towing company. We recommend checking the vehicle with a known technician for better inspection.

– Emission Warning Light Comes on in Honda Civic

If Honda Civic’s emission warning light has come on, remain calm and focused. First, understand the cause and try to fix the issue.

You can do it yourself if it’s a minor problem (like a loose gas cap). But if the problem seems troublesome, call a technician for help or a towing vehicle.


1. Can the Emission System Warning Light Be False?

Yes, the emission system warning light could be false in some cases. The sensor can (possibly) malfunction, leading to an incorrect reading and a false warning being sent to the driver. Sometimes, it can also turn on the light when you fill-up the gas tank recently.

This happens because the evaporating gas vapors from the tank will cause the alarm to be triggered.

2. Can Gas Mileage Be Affected by the Check Emission System Light?

Yes, your vehicle’s gas mileage can be affected by the check emission light. When this warning sign illuminates, it could mean your car isn’t running optimally, leading to a decreased fuel economy. It may also cause further damage and more expensive repairs if left unchecked.

So consult a certified mechanic or take your car to an auto shop immediately.

3. Is Check Emission System Warning Light Legal?

Yes, the check emission system warning light is legal. Most states require cars to pass an emissions test every two years to remain legal and roadworthy. While paying for repairs can be costly and inconvenient, these laws are designed with safety in mind and help protect our environment too.


Check emission system warning light is a crucial indicator of problems in your emission system.

Whenever it turns on, consider the following points:

  • The warning light can be turned on by a faulty emission system, mass air flow, particulate filter, or ignition system.
  • Notice whether it is continuously turned on or flashing rapidly to understand the severity.
  • Try to fix the issue to turn it off. Otherwise, you can also turn it off manually with some tricks.
  • Usually, fixing this warming light can cost between $50 to $200.
  • You can practice methods that prevent the light but don’t ignore it once it turns on.

Call a certified technician or a trusted auto shop for inspection and repair. Next time you see the check emission system light coming on, don’t panic and act quickly.

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