What it means
The lean NOx trap (LNT) on bank 1 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.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The NOx adsorber, also called a lean NOx trap, stores nitrogen oxides in the exhaust on bank 1 and releases them during regeneration. The control module evaluates its efficiency using downstream NOx sensor data or a model; P2000 sets when bank 1's adsorber falls below the required efficiency window, which can happen after sulphur buildup, thermal aging, or ineffective regeneration.
Common causes
Most likely first.
- Sulphur poisoning from high-sulphur fuel — desulphation regeneration not running
- Thermal aging of washcoat after high-temperature exposure
- Downstream NOx sensor reading drifts
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)
How to diagnose it
- Scan freeze-frame data and related emissions codes, then review bank 1 downstream NOx readings and regeneration history to see the conditions associated with the efficiency failure.
- Check for NOx sensor or regeneration-control faults that could make the monitor report poor bank 1 adsorber efficiency.
- Inspect the exhaust around the bank 1 adsorber and downstream NOx sensor for leaks, damaged wiring, or loose connectors that could distort readings.
- Compare bank 1 downstream NOx sensor response with the manufacturer's expected behavior and, where available, the corresponding bank's data.
- If sensor signals and exhaust integrity check out, verify that the manufacturer's specified desulphation or regeneration strategy is completing before condemning the bank 1 adsorber.
Common fixes
- Repair exhaust leaks or damaged wiring at the bank 1 adsorber and downstream NOx sensor.
- Restore the specified regeneration or desulphation operation if a control fault is preventing it.
- Replace the bank 1 downstream NOx sensor if testing confirms its reading has drifted.
- Replace the bank 1 NOx adsorber if testing confirms thermal aging or persistent efficiency loss.
Can I keep driving?
The vehicle may continue to run, but it can exceed NOx emissions limits and fail inspection; related warnings may lead to a no-start countdown on some vehicles. Arrange diagnosis promptly and heed any countdown or emissions-system warning.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.