OBD-II code · Powertrain (generic, extended)
P22F9 NOx Sensor Performance - Slow Response Low to High (Bank 1 Sensor 1)
NOx sensor on bank 1 sensor 1 responds too slowly when NOx concentration rises (typically observed when SCR dosing is reduced or stopped). The sensor has aged or its protection cap is clogged.
Is it safe to drive with P22F9?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelySensor aged or protection cap clogged
- Less likelySensor element aged beyond calibration window
- Less likelySensor element contaminated by oil, soot or coolant
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)
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1–3 h
- Emissions test
- Likely to fail
- Parts involved
- Nox Sensor
Related codes
- P22FCNOx Sensor Performance - Slow Response Low to High (Bank 1 Sensor 2)
- P22F6Cylinder 8 Alternative Fuel Injector Control Circuit Low
- P22F7Cylinder 8 Alternative Fuel Injector Control Circuit High
- P22F8Cylinder 8 Alternative Fuel Injector Control Circuit Range/Performance
- P22FANOx Sensor Performance - Slow Response High to Low (Bank 1 Sensor 1)
- P22FBNOx Sensor Performance - Sensing Element (Bank 1 Sensor 1)
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.