P2000
PowertrainNOx Trap Efficiency Below Threshold Bank 1
Your NOx adsorber catalyst on bank 1 isn't trapping nitrogen oxides as efficiently as the ECU expects. This is the lean-NOx-trap on diesels (different from AdBlue / SCR, that's a separate system).
ⓘ Information only. This page provides general educational information about fault code P2000. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P2000 mean?
P2000 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: NOx Trap Efficiency Below Threshold Bank 1.
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Engine warning light, often the only obvious symptom
- • Sometimes drivability is unaffected day-to-day
- • On some cars, eventual limp mode if the trap fails completely
- • Slightly worse fuel economy
Possible causes
Causes commonly associated with P2000, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Sulphur poisoning of the trap, sustained running on high-sulphur fuel degrades the catalyst material
- 2. Catalyst aging, traps eventually wear out, often around 100,000-150,000 miles
- 3. Failed NOx sensor reporting incorrectly (the cause is the sensor, not the trap itself)
- 4. Trap damaged by a misfire or rich-running event
- 5. Repeated regeneration interruptions
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Read live data from the upstream and downstream NOx sensors. A genuinely failed trap shows similar readings before and after, a healthy trap shows the downstream value much lower
- 2. Check whether you also have NOx sensor codes stored, those need fixing first
- 3. On some cars, a forced 'desulphation' procedure can be commanded with a scan tool, this purges sulphur from the trap and may restore function
- 4. If the trap is genuinely degraded, replacement is the only fix
Common questions about P2000
What's the difference between this and AdBlue / SCR? +
Lean-NOx-traps (LNT) are passive devices, they catch NOx during normal running, then the ECU briefly runs the engine rich to purge them. SCR systems use AdBlue (urea) injected into the exhaust to chemically convert NOx. Older diesels (broadly pre-2015) typically use LNT; newer ones use SCR; some use both. P2000 is specifically the LNT efficiency code.
Will it fail an MOT? +
The code itself doesn't cause failure but if the engine warning light is on at MOT time, that's an automatic fail under current rules for cars from 2018. Fix the underlying issue first.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →