P2001: NOx Adsorber Efficiency Below Threshold — Bank 2
What to do
If codes for both banks are stored, say so — a fault affecting both sides equally usually means fuel, driving pattern or a purge strategy rather than two devices failing at once, and those are much cheaper to address.
What this code means
The same conclusion as P2000, measured on bank 2. As with every paired bank code in the corpus, whether the two appear together is the most informative thing about them.
One bank alone points at something specific to that side — its NOx sensor, an exhaust leak on that manifold, or genuine deterioration of that trap. Both banks together point at something shared: fuel quality, a purge strategy that is not completing, or a driving pattern that never lets either trap clean itself. Shared causes are the more common and the cheaper of the two.
Likely causes
Start here
- Sulphur poisoning of the NOx adsorber · moderate
- Purge cycles not completing · moderate
- Faulty NOx sensor · moderate
- Predominantly short journeys · easy
Less common
- Failed NOx adsorber · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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