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  • Diagnostic trouble code (DTC) P0422 stands for “Catalyst 2 Efficiency Below Threshold (Bank 1).”
  • Once this error code is logged, it means that the emission efficiency of the catalytic converters in Bank 1 is below the minimum allowable limit.
  • The common causes of this error code include a bad catalytic converter, a malfunctioning oxygen sensor, or an exhaust leak. In some cases, internal engine damage can cause high oil consumption, triggering this error code.

There are many issues that could activate the Check Engine Light. If you get the OBD-II code P0422 after a quick scan, this could mean that there is an issue in your vehicle’s emission system. Read on to learn more about code P0422, the symptoms you should look out for, and the possible triggers of the code.

What Does the P0422 Code Mean?

Diagnostic trouble code (DTC) P0422 stands for “Catalyst 2 Efficiency Below Threshold (Bank 1).” It indicates that the emissions efficiency of Bank 1 catalytic converters are below the minimum allowable limit. This threshold is monitored by the catalyst monitor oxygen sensor, which is located near the catalytic converter’s outlet.

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The purpose of your car’s catalytic converter is to oxygenate the exhaust gasses and improve tailpipe emissions. It is monitored by the catalyst monitor oxygen sensor.

catalytic converter 2 1
The purpose of your car’s catalytic converter is to oxygenate the exhaust gases and improve tailpipe emissions.

The engine control module (ECM) tracks the switching frequency of the heated oxygen sensors 1 and 2 (front and rear sensors). A functional three way catalyst converter typically indicates a low switching frequency of heated oxygen sensor 2. The frequency increases as the converter deteriorates.

The P0422 code is logged when the frequency ratio of both heated oxygen sensors 1 and 2 reaches the threshold.

You can get more helpful information in our technical discussion about how cat converters work and catalytic converter efficiency.

What are the Common Causes of the P0422 Code?

Here are some common triggers of the error code P0422:

  • Defective catalytic converter
  • Defective oxygen sensor
  • Exhaust leak
  • Damaged catalytic converter due to engine misfires
  • Damaged catalytic converter due to a leaking head gasket
  • Internal engine damage leading to high oil consumption

What are the Possible Symptoms of the P0422 Code?

Depending on the severity, other related diagnostic trouble codes may also be stored. Expect an illuminated check engine light once the P0422 code is logged. In most cases, the engine code exhibits no other noticeable symptoms.

How to Diagnose the P0422 Code

Because the error code P0422 is generic, it is supported by various makes and models. This can make its diagnosis and repair difficult for the average DIYer. To help you understand and troubleshoot this error code better, check out the video below:

See also  Emission Control Systems

How to Fix the P0422 Code

Like most OBD-II codes, the P0422 code shares similar causes and symptoms with several other engine codes. However, resolving this error code takes more than just a generic solution. It’s better to leave the repairs to the experts if you aren’t confident in your automotive repair skills.

The code could be triggered by anything from a defective catalytic converter to a faulty oxygen sensor, so you must do your research thoroughly. Keep in mind that all vehicles are different. It’s important to always consult your owner’s manual and the factory repair information before DIY-ing any repairs.

Consult online auto repair sources for guidance. For instance, an ALLDATA subscription provides detailed factory repair information that you can use to accurately resolve issues in your car. This should help you resolve this error code and other fixes you may need to carry out in the future.

Get a Replacement Catalytic Converter that Fits Your Car

Replacing a faulty one usually costs a lot. It’s a good idea to stop driving your vehicle if you have a defective catalytic converter to avoid creating more problems in the exhaust system. As for the bad catalytic converter, you can easily order a replacement here at

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Enjoy the convenience of shopping online for a new catalytic converter with Plug your vehicle’s year, make, model, and engine into our website’s selector, and the search results will show the parts that fit your application. It takes only several clicks or taps to complete your order, and our products will ship from the distribution center nearest you. If you live in the continental U.S. and order before noon ET, your new catalytic converter can arrive at your doorstep in as little as two business days. You won’t have to worry about the quality of our parts, either, since we only source our products from trusted brands.

Why wait until the catalytic converter fails when you can easily order one from Shop for our products today and choose a part that fits your application!

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About The Authors
Written By Automotive and Tech Writers

The Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Technical Reviewer at

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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