P2001NOx Adsorber Efficiency Below Threshold (Bank 2)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- P2001 belongs to the second cylinder bank: the NOx storage catalyst fed by bank 2 has lost so much capacity that it no longer holds and reduces the nitrogen oxides of lean running. The code is only possible on V or boxer engines that give each bank its own trap. No manufacturer documents P2001 publicly; the best documented trap application, the inline-six 6.7 L Cummins in Ram pickups, has a single bank and reports P2000. CARB sets the same emission-based limit for every NOx adsorber, so the bank 2 monitor works like its bank 1 sibling, comparing what the sensors behind the trap see during storage and purge with a model. Usual suspects are sulphur that desulphation can no longer burn off, a heat-damaged coating, misreading sensors on that side or purges cut short. The car keeps driving normally.
- What you may notice
- Malfunction indicator lamp on
- Driveability usually unchanged
- Likely causes
- LikelyBank 2 NOx trap poisoned by sulphur or thermally aged
- PossibleOxygen or NOx sensor on bank 2 reading wrongly
- RareRich purges on bank 2 repeatedly interrupted
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €100 – €3,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.