OBD-II code · Powertrain (generic, extended)
P2001 NOx Adsorber Efficiency Below Threshold (Bank 2)
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.
Is it safe to drive with P2001?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelySulphur poisoning
- PossibleThermal aging of washcoat
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)
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 2–6 h
- Emissions test
- Likely to fail
- Parts involved
- Nox Adsorber Catalyst, Nox Sensor Downstream
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.