P22FBNOx Sensor Performance - Sensing Element (Bank 1 Sensor 1)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- P22FB questions whether the measuring element of the front NOx sensor on bank 1 still reads true. GM's 2025 diesel tables hold its filtered value against modelled engine-out NOx and fail it below minus 36 % or above plus 77 % (version A) or outside minus 51 to plus 100 % (version B), as a Type A fault with the MIL in one trip. Volvo and Mack count P22FB-92 among the codes that mean a damaged inlet sensor. Software was behind many cases: Isuzu N-Series, Hino S-Series and Chevrolet Low Cab Forward trucks with the 5.2L 4HK1 got new DEF control unit calibrations, and GM 23-NA-213 pairs P22FB with P0402 on the 2024 6.6L L5P. Mazda's 2018 to 2019 CX-5 SKYACTIV-D stored it for a cancelled self-check (01-004-22). P22FE is the rear sensor.
- What you may notice
- Check engine light on, on GM's 2025 diesels already after one drive
- Rough idle or surging if an EGR fault is behind it
- Often no other noticeable effect
- Likely causes
- LikelyMeasuring cell of the front NOx sensor drifted or damaged (Volvo/Mack P22FB-92)
- PossibleECM or DEF control unit software, fixed by reprogramming (Isuzu SB22-L-001, GM 23-NA-159, Mazda 01-004-22)
- PossibleReal engine-out NOx differs from the model, e.g. through an EGR fault (P0402)
- RareExhaust leak ahead of the sensor
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €0 – €1,100
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.