Powertrain, generic (extended)

P22FB NOx Sensor Performance - Sensing Element (Bank 1 Sensor 1)

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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.

Likely causes

Measuring cell of the front NOx sensor drifted or damaged (Volvo/Mack P22FB-92)
ECM or DEF control unit software, fixed by reprogramming (Isuzu SB22-L-001, GM 23-NA-159, Mazda 01-004-22)
Real engine-out NOx differs from the model, e.g. through an EGR fault (P0402)
Exhaust leak ahead of the sensor

Symptoms

  • 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

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€0–1,100
Time0.3–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

nox sensor

Related codes

P22FEP2201P22F9P22FAP0402

References: gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov, static.nhtsa.gov.