P22FB NOx sensor performance, sensing element (bank 1 sensor 1)
What P22FB means
Diesel engines with AdBlue use NOx sensors to measure exhaust NOx before and after the SCR catalyst. P22FB means the sensing element of the upstream sensor (bank 1 sensor 1) is not performing as expected. AdBlue dosing becomes less accurate, and a start-restriction countdown can follow on some cars.
P22FB is a generic SAE J2012 code: it means the same on every make. The exact cause still depends on the car, so read the freeze-frame data before replacing parts.
At a glance
- Severity
- Medium
- Typical repair cost
- 400–1500 €
- Workshop time
- 1–3 h
- Repair difficulty
- Hard
- DIY possible
- No
- Check engine light
- Yes
- Affects emissions test
- Yes
Parts and labour at an independent workshop in Europe. Main dealers charge more; the cause decides the bill, not the code.
Symptoms
- Check engine or AdBlue/NOx warning light
- Possible start-restriction countdown
- Reduced power on some cars
- Technical inspection failure for NOx
Common causes
- Failed NOx sensor element
- Sensor contaminated by soot or oil
- Damaged sensor wiring or control unit connector
- Exhaust leak near the sensor
- Engine fault (EGR or injector) giving unusual NOx readings
Can I keep driving with P22FB?
You can drive, but have it checked within one or two weeks. If an AdBlue countdown appears, repair it before the countdown ends.
What to check first
- Check for EGR, injector or exhaust leak faults that affect NOx readings
- Inspect the NOx sensor wiring and its control unit connector
- Compare upstream NOx readings with expected values in live data
- Replace the NOx sensor (usually supplied with its control unit) if confirmed faulty
Related codes
- P2293 Fuel pressure regulator 2 (B) performance
- P2291 Injector control pressure too low during cranking
- P2400 EVAP leak detection pump control circuit/open
- P2418 EVAP system switching valve control circuit/open
- P2459 Diesel particulate filter regeneration frequency (bank 1)
- P2463 Diesel particulate filter restriction, soot accumulation (bank 1)
- P218F Reductant (AdBlue) no flow detected
- P2101 Throttle actuator control motor circuit range/performance
Data: TORKO fault-code catalogue, built on OBDex (CC0-1.0) and reviewed against workshop practice. Informational only — it does not replace a diagnosis by a mechanic.
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