P2001: NOx Adsorber Efficiency Below Threshold (Bank 2)
Standardized SAE J2012 code · P20xx — Fuel & air metering and auxiliary emission controls
What does P2001 mean?
The lean NOx trap (LNT) on bank 2 is no longer storing or releasing NOx within the required efficiency window. Detected by the downstream NOx sensor or model-based monitor — typically caused by sulphur poisoning, thermal aging, or a failed regeneration strategy.
The code tells you which monitor failed, not which part is broken. Test before replacing parts.
Symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
Common causes
- High Sulphur poisoning
- Medium Thermal aging of washcoat
Likelihood is a general estimate across vehicles; your make and model may differ.
Add your car to see reports of P2001 on the same make and model first.
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