NOx GPM Emissions Fail: Causes and Fixes

Excess emission of nitrogen oxides from auto combustion engines is dangerous. These oxides can contaminate the healthy air we breathe in. These nitrogen oxides are from harmful emissions from the old fuel injection cars. With modern NOx-control technologies, releases of this exhaust have largely reduced.

Yet, cars still fail emission test. A few reasons are responsible for a failed standard emission test, and I will talk about that shortly. The NOX emission Test Failure occurs from lean conditions, engine overheating, clogged EGR, and many more.

In this article, I’ll explain what NOx emission means, what causes it to fail, and the remedies to apply.

What is NOx GPM Emissions Test

NOx Emissions Test is like a report card for your car’s cleanliness. Failing to attend to it might hurt the environment. Let’s find out why and what we can do about it.

Emissions tests, also called smog checks, reveal the pollutants in a vehicle’s exhaust. It helps control the amount of greenhouse gases escaping into the atmosphere. Each state has a legal limit that all cars must pass before they’re legally allowed to operate in the neighborhood.

To carry out an emissions test, you’ll need a qualified technician. The job is to plug your car into a testing system using the vehicle’s onboard diagnostic port (OBD2 port).

NOx fully means Nitric oxide (NO) and nitrogen dioxide (NO2). Nitrogen oxides are a family of very poisonous and reactive gases. They form when fuel burns at a high temperature and naturally by lightning. So diesel or petrol engines are all culprits in introducing nitrogen oxides into the atmosphere.

GreenHouse gases and pollutants like Carbon monoxide in car exhaust are very harmful to human health and the environment if consumed on a large scale. However, they also form when there is a lightning strike.

In the Volkswagen 1960 era, authorities have been regulating the NOx emissions of vehicles, and several things can make a vehicle fail the test. Therefore, passing an emissions test is very important. In this article, I will discuss the causes of a NOX GPM Emissions test failure and how to fix it.

What Causes a NOx Emission Test Failure

NOx (Nitrogen Oxide) emissions failing in a vehicle can be caused by several factors, and addressing them typically involves a combination of diagnostics and repairs. A massive buildup of carbon deposits in the combustion chambers is a culprit. Incorrect ignition timing can cause a high level of NOx gas in the vehicle exhaust

Now, let us talk about these in detail.

Faulty or Clogged EGR Valve

The job of the EGR system is to redirect a small amount of exhaust gas back into the intake manifold to reduce the temperature in the combustion chambers. Once it is faulty, the combustion chambers will heat up, and as soon as the heat reaches 2500F, it begins to produce NOx gas.

A faulty catalytic converter

Some vehicle manufacturers do not include EGR valves in their products. In cars like this, the catalytic converter decreases the production of NOx gasses. Immediately, if it develops a fault, the car will most likely produce a lot of NOx gasses.

Inadequate air-fuel mixture

Your car may also suffer NOx GPM emission failure if there’s an improper or inadequate mixture of air and fuel.

High engine mileage

The higher the vehicle’s mileage, the more carbon its engine builds over the years in the combustion chambers. Carbon build-ups decrease space for the combustion of air and fuel. They cause higher cylinder compression and high temperature. The more compression the build-ups cause, the more combustion they produce.

Faulty oxygen sensors

Oxygen sensors monitor the air-fuel ratio in the exhaust gases. If they malfunction, the engine may run too rich, leading to increased NOx emissions.

How to Fix NOx Emissions Test Failure

Have you taken an emissions test, and your car failed? Or perhaps you are thinking of taking a test soon; this section will help you to know how to fix problems that result in high levels of NOx gasses.

Check the EGR system

A faulty EGR valve can cause high NOx levels by not properly recirculating exhaust gases. Clean or replace the EGR valve if needed.

Replace the oxygen sensor

A faulty oxygen sensor can trick the engine computer into running too lean, increasing NOx emissions. Replace old or malfunctioning O2 sensors.

Do a fuel injector cleaning service

Clogged or dirty fuel injectors can cause improper fuel mixing, also increasing NOx. Have injectors professionally cleaned.

Check for air leaks

Any leaks in intake manifold, hoses, etc. can introduce extra air and cause high NOx. Inspect all connections and seals and repair any leaks.

Adjust air/fuel mixture

A rich air/fuel mixture can help lower NOx emissions. A mechanic may be able to adjust computer settings to richen the mixture.

Use higher cetane fuel

Higher cetane fuels, like premium diesel, burn more completely and produce less NOx. Using a higher grade may help.

Check the turbocharger

A faulty turbo not providing proper boost can lead to increased NOx. Check and replace the turbo if needed.

Perform a diesel particulate filter (DPF) reset

A full DPF can force engine adjustments leading to more NOx. Reset the DPF if it is full.

Replace catalytic converter

If no other fixes work, the catalytic converter may need to be replaced to properly treat exhaust.

Why Take an Emissions Test?

The emission test is important as it helps reduce the level of greenhouse gases and pollutants. Ultimately, humans benefit greatly. from this process. However, there are also benefits for car owners because your car will always be in good working condition, extending your vehicle’s life span. Also, emissions tests take only 15-30 minutes, depending on each state’s requirements.

Final Thoughts

You shouldn’t allow your car to fail the NOx emission test to avoid running afoul of the Clean Air Act Amendments. Don’t forget, the main object of the Amendments is to reduce NOx emissions. The law expects you to run an emission test on your car once every two years. But it depends on the law in the state you live in and your car’s fuel type. By regulation, you should schedule your car for the test once it hits six years and above on the road.

Finally, before heading out to take your car’s NOx Emissions Test, it is important to know the legal requirements or information. While all states may have an adjustment in their respective requirements, some documents you’ll likely need are:

  • Renewal notice probably via email, eNotify, or your mail
  • Your vehicle certificate of registration
  • Prior inspection report

Hope this article helps you make an informed decision on NOx emission testing.

  • James Smith

    I'm James Smith, a car enthusiast and a content writer for Daily Car Tips. I have a passion for all things cars, from classic muscle cars to the latest electric vehicles. When I'm not writing about cars, you can usually find me tinkering with my car or checking out the latest automotive trends.

    View all posts

Related Posts