OBD-II code · Powertrain (generic, extended)
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.
Is it safe to drive with P22FA?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelySensor aged
- 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
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Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.