P2000 Code: NOx Adsorber Efficiency Below Threshold Bank 1

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.

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.

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.

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?

• Faulty oxygen sensor or NOx sensor
• Bad or overloaded NOx adsorber catalyst
• Faulty mass air flow sensor
• Exhaust or intake leaks
• Circuit issues, such as a damaged wire or poor connection
• A PCM issue, such as software in need of an update

What are the Common Symptoms of P2000 Code?

• Illuminated check engine light

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.

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.