P2001 Code: NOx Adsorber Efficiency Below Threshold Bank 2

Reviewed by

William Guzenski, ASE Certified Master Automobile Technician

Contact Center Manager and Technical Reviewer at CarParts.com

Written by CarParts.com Research Team - Updated on October 2nd, 2023

Reading Time: 3 minutes
Summary
  • The P2001 code stands for “NOx Adsorber Efficiency Below Threshold Bank 2,” which means the powertrain control module detects that the Selective Catalytic Reduction (SCR) system isn’t performing its job properly.
  • A faulty oxygen sensor or NOx sensor, an overloaded NOx adsorber catalyst, and a faulty mass air flow sensor are some common causes of the P2001 code.
  • An illuminated check engine light is one of the common symptoms of the P2001 code.

Diesel-powered engines are equipped with a Selective Catalytic Reduction (SCR) system that uses Diesel Exhaust Fluid (DEF) to reduce nitrogen oxide (NOx) emissions. When there are problems with the SCR system, it can trigger the P2001 code or other related trouble codes. You should use a scan tool to check if your vehicle has stored these codes, as they can help you diagnose the issue.

What Does the P2001 Code Mean?

The P2001 code is defined as NOx Adsorber Efficiency Below Threshold Bank 2. The powertrain control module triggers the P2001 code when it detects that the SCR system isn’t performing its job properly. This code can be triggered when your vehicle’s nitrogen oxide (NOx) sensors detect higher levels of NOx in the exhaust. This code indicates that this problem is present in engine bank #2.

The P2001 code can be triggered when your vehicle’s nitrogen oxide (NOx) sensors detect higher levels of NOx in the exhaust.

Note: The definition of the P2001 code can 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 P2001 Code?

The P2001 code is typically triggered when your vehicle has the following problems:

What are the Common Symptoms of the P2001 Code?

Common symptoms associated with code P2001 include the following:

An issue with the MAF sensor can also result in a P2001 code.

How to Diagnose the P2001 code

If the P2001 code has been triggered, then you need to identify the cause of the diagnostic trouble code (DTC) before you make any repairs. You shouldn’t automatically assume that your vehicle has the same problems as the common causes of the P2001 code.

Diagnosing DTCs typically involves doing visual inspections and perhaps even tests on some components. This task can require technical knowledge and specialized tools. If you think this is daunting, then you should leave it to a professional mechanic.

How to Fix the P2001 Code

Want to solve the problems triggering the P2001 code? Unfortunately, there isn’t a single procedure that will guarantee a fix. There’s a chance that your vehicle might not experience any reliability or drivability symptoms with this trouble code. However, this shouldn’t stop you from fixing this DTC, especially considering that your vehicle will produce more emissions and pollution when this problem persists. We recommended that you fix the issues triggering this code to prevent any future problems.

Your course of action will depend on the diagnosis. That’s why getting an accurate diagnosis is important. Once you’ve found the root cause, you can start looking at reputable internet repair resources and how-to guides for possible solutions. Also, make sure to check your owner’s manual because it might have important information regarding your problem.

If you don’t have much experience diagnosing or fixing error codes, then you should consult a professional mechanic.

About The Authors
Reviewed By William Guzenski, ASE Certified Master Automobile Technician

Contact Center Manager and Technical Reviewer at CarParts.com

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.

Written By CarParts.com Research Team

Automotive and Tech Writers

The CarParts.com 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 CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

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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CarParts.com Research Team and William Guzenski, ASE Certified Master Automobile Technician