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The nitrogen oxide (NOx) sensor is used by the powertrain control module (PCM) to monitor the performance of the reductant system, making sure that NOx emissions are being controlled effectively. If the PCM is unable to detect a signal from the NOx sensor, a P2202 trouble code will be logged by on-board diagnostics (OBD).

What Does the P2202 Code Mean?

Diagnostic trouble code (DTC) P2202 stands for “NOx Sensor Circuit Low Bank 1.”

Diesel engines require high combustion temperatures to effectively burn fuel, which means they tend to emit a large amount of NOx. To counter the effects of harmful emissions, diesel engines are equipped with an exhaust gas recirculation (EGR) system.

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The EGR system reroutes a certain amount of exhaust gas to the combustion chamber, cooling the combustion flame and preventing NOx formation.

car diesel and def fill inlet
Diesel engines also have diesel exhaust fluid (DEF) that’s injected into the exhaust stream before the selective reduction catalyst, converting emissions into harmless gases.

Diesel engines also have diesel exhaust fluid (DEF) that’s injected into the exhaust stream before the selective reduction catalyst, converting emissions into harmless gases. During this process, NOx is broken down into nitrogen, carbon dioxide, and water.

NOx sensors are typically placed at the inlet and outlet sides of the selective oxidation catalyst. The sensors measure the amount of NOx in the exhaust after passing through the emissions equipment.

Note: The definition of code P2202 might be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the P2202 Code?

What are the Common Symptoms of the P2202 Code?

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How to Diagnose the P2202 Code

DTC P2202 can be logged in vehicles with an OBD-II system. However, keep in mind that the steps for diagnosis can vary, depending on vehicle specifications. Diagnosing trouble codes like this one usually involves using a scan tool and conducting visual inspections. If you’re unsure of what to look for, it’s best to have your vehicle checked by a mechanic instead.

But if you’ve had some experience with diagnosing trouble codes, then you can go ahead and do it yourself. To help you out, here is a video that demonstrates what the process might involve:

How to Fix the P2202 Code

Attempting to fix a P2202 trouble code can be confusing without the right tools and technical knowledge. Under these circumstances, it’s best to take your vehicle to the nearest repair shop and have a trained professional perform the necessary repairs. This will ensure that all steps and protocols are followed correctly.

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But if you think you’re well-versed with automotive repair and can handle resolving the issue on your own, make sure you’re consulting the right guides. There’s no such thing as an umbrella fix that will work for all makes and models, so you might want to check out guides like those from Chilton or an ALLDATA subscription to get vehicle-specific repair information.

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 Contact Center Manager and Technical Reviewer at

William “Bill” Guzenski has produced hundreds of how-to videos for the automotive community. He’s an ASE Certified Master Automobile Technician, and is affiliated with the Specialty Equipment Market Association (SEMA). He loves attending race events and car shows throughout the country, as well as traveling in his 40-foot motorhome, exploring abandoned mines and ghost towns.

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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