Powertrain
generic / SAE
P22FA
NOx Sensor Performance - Slow Response High to Low (Bank 1 Sensor 1)
NOx sensor on bank 1 sensor 1 responds too slowly when NOx concentration falls (typically observed when SCR dosing increases). The sensor has aged or its protection cap is clogged.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number2 / FA
Possible causes
- Sensor aged high
- Sensor element aged beyond calibration window low
- Sensor element contaminated by oil, soot or coolant low
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)
Inspection / repair
- Difficulty: hard
- DIY: shop recommended
- Estimated cost: 400–1500 €
- Estimated time: 1–3 h
- Component: nox sensor
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012