What Is Honda Odyssey Emissions System Problem? Causes & Fixes

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 If you are here, you probably have “the emissions system problem” warning popping up on the dashboard, or you probably failed the emission test. The warning indicates problems with the emission system. If left unfixed, it can lead to increased emissions and decreased fuel efficiency, and the vehicle will not be compliant with emissions regulations.

This is a one-stop guide for this issue; you will find out everything you need, including what causes the issue and how to fix it. 


What Is the Emissions System?

The emission system is present in most modern cars, including the Honda Odyssey; its function is to reduce harmful pollutants emitted from the vehicle’s engine into the atmosphere. The system uses several components such as Oxygen Sensors, Exhaust Gas Recirculation (EGR)Catalytic ConverterEvaporative Emission Control System (EVAP)and more to do its job.


Why Does Honda Odyssey Show Emissions System Problem Warning?

As mentioned in the intro, the “Emissions System Problem” warning indicates problems with the emission system. The cause can be as simple as a loose gas cap or a failing catalytic converter. So, for some people, DIY solutions can fix the issue, while others may have to take the van to a mechanic’s shop. 


How to Fix It?

Since the Emissions system works with the help of several components, the problem can have multiple causes. For some people, the problem can result from a loose gas cap, and for others, it can be something big. Below, I have covered all the solutions to fix the issue and get rid of the warning.


Solution 1) Check for Loose Gas Cap

The car has an EVAP system that captures and stores fuel vapor from the gas tank and prevents it from releasing into the atmosphere. To capture the fuel vapor, the EVAP creates a vacuum in the fuel tank. Without the vacuum, it will not function effectively.

So, if your Van’s gas cap is loose, it will cause a vacuum leak that would prevent the EVAP system from capturing fuel vapor and would result in the “Emissions System Problem” popping up on the screen. 

Check if the gas cap is loose; if it is, make sure you screw it on tightly. If the cap is not screwing tightly, get it replaced. 


Solution 2) Clean or Replace the Air Filter

While the air filter cannot directly cause the issue, a clogged or dirty air filter can prevent proper airflow to the engine, resulting in an imbalance of the air-to-fuel ratio. This leads to incomplete combustion of fuel, which causes too much production of pollutants. 

The emission system can pick these pollutants, and the warning will be triggered due to increased emissions. 

If that is your situation, too, clean the filter; if it’s way too dirty to the extent that it cannot be cleaned, replace it.


Solution 3) Inspect Oxygen Sensors

One oxygen sensor is called the Upstream Oxygen sensor. It is located in the exhaust manifold or in the exhaust pipe near the exhaust manifold; the location can be slightly different depending upon the make and model of the Honda Odyssey. 

The sensor measures oxygen levels in the exhaust gases right before entering the catalytic converter. Then, the data is used by the Engine Control Unit (ECU) to adjust the air-fuel mixture for combustion efficiency.

The other sensor is the Downstream Oxygen Sensor, which is located 

after the catalytic converter. It monitors oxygen levels in the exhaust gases after passing through the catalytic converter. The data is also used by the Engine Control Unit (ECU) to determine catalytic convert’s health. 

If any sensor stops working, it would cause the warning to pop up on the dashboard. Ensure you check the sensors and replace any ones that are not working. 


Solution 4) Check the Catalytic Converter

The Catalytic Converter’s job is to reduce harmful emissions before they are released into the atmosphere. A failing Catalytic Converter would be unable to do its job, and the Check emissions warning light will pop up on the dashboard. 

Make sure you inspect the Catalytic converter properly; if you cannot do it on your own, get it checked by a mechanic. 


Solution 5) Inspect the Exhaust

A leaking exhaust lets harmful pollutants release into the atmosphere, which can lead to increased emissions. It can also cause issues such as incomplete combustion. Make sure you carefully inspect the exhaust for damage and get it repaired or replaced. 


Solution 6) Replace the EGR Valves

The EGR system recirculates the engine’s exhaust gases into the combustion chamber to help lower combustion temperatures and reduce the formation of nitrogen oxides (NOx).

If the EGR valves are failing, you will face emission issues, so get the EGR valves replaced and make sure you keep the passages clean, too. 


Solution 7) Replace the Purge Valve

This valve regulates the flow of fuel vapors from the charcoal canister into the engine’s intake manifold. A damaged or malfunctioning 

A damaged or malfunctioning will cause emission issues, so if that is the case with you, make sure you take the car to a mechanic and replace it. 


Solution 8) Replace Fuel Injectors 

Malfunctioning fuel injectors can usually cause issues like imbalanced air-fuel mixture and incomplete combustion, which leads to emission-related problems. 

Replacing the injectors will fix the issue, and the warning will disappear.



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