Maintenance Tips, Tricks And Hacks For Your Vehicle

Will Catalytic Converter Cleaner Fix P0420? (Answered!)




Many car owners experience problems with the catalytic converter (P0420). Since catalytic converters can be quite expensive, many owners ask if a Catalytic converter cleaner will fix a P0420. It is a legitimate question.

In my opinion, before you change any part of your vehicle, you first need to see if a good cleaning will fix the problem. But, many times, the catalytic converter cleaners state that their products can fix a P0420 code.

Eager to find out more about this matter, I talked to a couple of mechanics who actually used catalytic converters in the past. Here is what I found out.

Key Takeaway

  • A catalytic converter cleaner can potentially fix a P0420 code if the issue is due to a clogged converter; however, it will not fix underlying mechanical issues causing the inefficiency.
  • The check engine light may go off after cleaning the catalytic converter if the light was triggered by issues related to the converter, but if the light persists, it could indicate more severe problems that a cleaner can’t address.

Will Catalytic Converter Cleaner Fix P0420?

Will Catalytic Converter Cleaner Fix P0420

Yes. If your catalytic converter is clogged up and the scan tool is showing a P0420 code, a catalytic converter cleaner will fix the problem.

The catalytic converter gets clogged up by unburnt fuel going into the exhaust system, or oil or antifreeze making their way into the exhaust system and creating a thick carbon and soot which easily clogs up the air passages.

A cleaner will clear the air passages inside the catalytic converter’s ceramic honeycomb and will fix the P0420 code.

Before you replace the catalytic converter which is a really expensive part, you might try cleaning it out first. When an inefficient catalyst code pops up (P0420), it can come up when you only lose 5% of its efficiency. The catalytic converter could still be working at 94% efficiency and it’ll trip the code. So, a little cleaning can often fix them.

A clogged catalytic converter can overheat your engine because the exhaust gases are unable to pass through the catalytic converter and out of the exhaust pipe. Instead, they are staying inside the engine for a bit longer than they should, therefore making it run a bit hotter.

There are a lot of catalytic converter cleaners, but I have used the Motorkote brand which I got from

The best way to clean a catalytic converter is to pour the catalytic converter into a full gas tank and either drive the car for about 150 miles at higher speeds or run the engine at about 2,500 RPMs for about 30 minutes.

That should be enough for the cleaner to run through and burn the impurities out of the catalytic converter and make it work again.

Will The Check Engine Light Go Off After Cleaning The Catalytic Converter?

Will Catalytic Converter Cleaner Fix P0420 (Answered!)

Yes. When the catalytic converter gets clogged up, it triggers an error code P0420 which is displayed as a check engine light on the dashboard. However, when you clean the catalytic converter and fix the issue, the vehicle computer will run tests and if cleaning the catalytic converter solved the issue, the check engine light will go off.

The catalytic converter plays a huge role. It cleans the exhaust gases from the combustion chamber before releasing them into the atmosphere. In many states, it is actually illegal to drive with a bad catalytic converter.

So, being exposed to exhaust gases all the time, the catalytic converter usually gets clogged up after 50,000 miles. When it does get clogged up, it triggers a check engine light and a P0420 code.

It takes for a catalytic converter to fail two times to trigger the check engine light on the dashboard. By cleaning the catalytic converter and actually fixing the problem, it will take the catalytic converter up to 40 passes for the computer to turn off the check engine light.

The catalytic converter has a honeycomb made out of platinum, palladium, and rhodium. These metals filter out harmful exhaust gases before releasing them into the atmosphere. Over time, the honeycomb gets carbon deposits to build up on it and stops working correctly.

The hot exhaust gases can’t pass through the catalytic converter and stay in the engine for a longer period which can it to overheat. This immediately triggers a check engine light (P0420 code) and has to be fixed immediately.

In most cases, cleaning the catalytic converter will fix the issue and will make the check engine light go off says Bob Is The Oil Guy.

Can I Drive My Car With a P0420 Code?

Yes. You can drive your car with a P0420 code. However, you will experience sluggish engine performance and reduced acceleration. Often, you will see dark exhaust smoke from the tailpipe and a smell of sulfur or rotten eggs. Plus, vehicles with a P0420 code can’t pass the emission test because the catalytic converter isn’t working properly and isn’t filtering out harmful exhaust gases.

All the harmful exhaust gases that exit the engine and pollute the environment go through the catalytic converter. The catalytic converter is built from precious metals that cause chemical reactions and they change the harmful gases into less harmful gases before releasing them into the atmosphere.

Driving with a bad catalytic converter and a P0420 code means that you are deliberately polluting the environment. The only scenario where it is okay to drive your car with a P0420 code is to the repair shop.

Driving your vehicle with a P0420 code is not going to be the same. The exhaust gases that are meant to go through the catalytic converter and out of the exhaust pipe won’t be able to do so. Instead, they will get to the catalytic converter and bounce back into the engine. This means that at this point, your engine has more hot exhaust gases in it and can overheat at any moment.

Symptoms like sluggish engine performance and reduced acceleration are often present when the catalytic converter is bad. While in reality, you can drive your car with a P0420 code, the experience won’t be the same. Many times you will notice black smoke out of the tailpipe and a rotten egg smell. Plus, if your vehicle is up for an emissions test, rest assured that it will fail it.


Q: What is a P0420 code?

A: The P0420 code is a generic powertrain code that indicates a problem with the efficiency of the catalytic converter. It is typically triggered when the computer detects that the catalytic converter is not performing as efficiently as it should be.

Q: What are the symptoms of a bad catalytic converter?

A: Some common symptoms of a malfunctioning catalytic converter include a decrease in engine performance, reduced fuel efficiency, the smell of rotten eggs coming from the exhaust, and the illumination of the Check Engine Light.

Q: How can I diagnose a faulty catalytic converter?

A: Diagnosing a faulty catalytic converter usually requires the use of professional diagnostic equipment. A mechanic can perform a series of tests, including checking the oxygen sensor readings and conducting a back pressure test, to determine if the catalytic converter is functioning properly.

Q: Can a catalytic converter cleaner damage my vehicle?

A: If used according to the manufacturer’s instructions, a catalytic converter cleaner should not damage your vehicle. However, it is important to use the cleaner specifically designed for catalytic converters and follow the recommended dosage. Using the wrong cleaner or applying too much can potentially cause harm to the catalytic converter or other components of the exhaust system.

Q: How often should I use a catalytic converter cleaner?

A: The frequency of using a catalytic converter cleaner depends on various factors, such as the age and condition of your vehicle, driving habits, and fuel quality. It is generally recommended to use a cleaner every 3,000 to 5,000 miles or as indicated in the product instructions.

Q: Can a clogged catalytic converter cause engine misfire?

A: Yes, a clogged catalytic converter can cause engine misfire. When the catalytic converter becomes blocked or restricted, it can lead to back pressure in the exhaust system. This increased pressure can disrupt the proper combustion process and result in engine misfires.

Q: What are some tips to prevent catalytic converter failure?

A: To help prevent catalytic converter failure, it is important to maintain your vehicle and address any potential issues promptly. Regularly servicing your vehicle, using high-quality fuel, and avoiding harsh driving conditions can all contribute to the longevity of your catalytic converter.

Q: Can I drive with a bad catalytic converter?

A: It is generally not recommended to drive with a bad catalytic converter. A malfunctioning catalytic converter can negatively impact your vehicle’s performance and fuel efficiency. Additionally, driving with a faulty catalytic converter may result in increased emissions, which can lead to environmental harm and potential legal consequences in areas with strict emissions regulations.

Q: Can I replace the catalytic converter myself?

A: While it is technically possible to replace the catalytic converter yourself, it is a job that is best left to professional mechanics. Replacing a catalytic converter requires specialized knowledge and equipment. It is important to ensure that the replacement part is the correct fit and meets the necessary emissions standards.

In Conclusion

When it comes to resolving the P0420 code, a catalytic converter cleaner can be an effective solution to restoring the efficiency of your car’s exhaust system.

The right combination of products, maintenance, and patience will help you get back on the road with improved performance and fewer emissions.



Vide Polowenski, Senior Mechanic

The information in this article is current and up-to-date in accordance with the latest mechanic SOPs.

Please take the time to leave a comment if this article has helped you in any way, you need additional help, or you have a suggestion.

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