NOx Adsorber Efficiency Below Threshold (Bank 1)
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.
Affected components
- Nox adsorber catalyst
- Nox sensor downstream
- Exhaust temperature sensor
Common causes
- High likelihood: Sulphur poisoning from high-sulphur fuel — desulphation regeneration not running
- Medium likelihood: Thermal aging of washcoat after high-temperature exposure
- Medium likelihood: Downstream NOx sensor reading drifts
Possible 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)
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- A drive cycle may be required after repair
Related codes
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.