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  • NOx sensors monitor nitrogen oxide levels in exhaust gases before and after going through the NOx trap. Code P2000 is set once the efficiency of the bank 1 adsorber falls below design parameters.
  • Some of the common causes of a P2000 code include a bad oxygen sensor, a faulty NOx sensor, and an overloaded NOx adsorber catalyst.
  • Your check engine light will illuminate once this code is logged.

The engine aftertreatment system plays a vital role in the emission control system of many diesel vehicles. It keeps track of the amount of oxygen in the exhaust gases produced by the engine as a byproduct of burning fuel to produce power. The readings go to the powertrain control module (PCM), which tweaks the fuel mixture entering the intake air to correct the engine running lean or rich.

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If the PCM notices that the nitrogen oxide (NOx) adsorber isn’t performing as well as it should, it will set a P2000 code.

What Does the P2000 Code Mean?

The diagnostic trouble code (DTC) P2000 indicates “NOx Adsorber Efficiency Below Threshold Bank 1.”

Many diesel vehicles have catalytic converters. However, cat cons are less effective because spent exhaust gases from diesel engines contain more oxygen.

automotive nitrogen oxide sensor image
If the PCM notices that the NOx adsorber isn’t performing as well as it should, it will set a P2000 code.

To help the catalytic converter reduce emission levels, diesel vehicles also have a NOx adsorption system. Also called a NOx trap, it’s part of the selective catalytic reduction (SCR) system.

The NOx adsorber is made of a material that attracts and stores nitrogen oxides. When exhaust gases pass through the adsorber, the NOx gets captured.

Like the EVAP canister in gasoline vehicles, the NOx adsorber can only store so much emission. An electronic injection system refreshes the adsorber by spraying it with reductant fluid, usually diesel fuel.

NOx sensors measure the nitrogen oxide level in exhaust gases before and after going through the NOx trap. They send their readings to the PCM.

See also  P20EE Code: SCR NOx Catalyst Efficiency Below Threshold (Bank 1)

The PCM will set the generic powertrain code P2000 if the bank 1 adsorber works far less efficiently than designed. We recommend avoiding performing a mobile desoot of the diesel vehicle until this problem is resolved.

Note: The definition of code P2000 can differ according to the vehicle manufacturer. Check the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the P2000 Code?

What are the Common Symptoms of P2000 Code?

image of an oxygen sensor
A faulty oxygen sensor or NOx sensor is one of the common causes of logged P2000 code.

How to Diagnose the P2000 Code

P2000 is a generic powertrain code that can show up in various makes and models. Various factors can change the root cause and symptoms among cases.

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If you don’t think you can run diagnostics on the P2000 code, you should bring your vehicle to a professional mechanic. Otherwise, you can go ahead and diagnose the issue yourself.

How to Fix the P2000 Code

Fixing a P2000 code’s underlying issues can become a tough task if you don’t have the right tools and know-how to evaluate the NOx adsorber for problems. Generally, it’s best to leave the job to professionals whom you trust.

For DIYers with advanced technical knowledge and hands-on experience who prefer to test and replace their vehicle on their own, it’s a good idea to consult the vehicle’s repair manual or look for an online repair database.

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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