Powertrain, generic (extended)

P22FA NOx Sensor Performance - Slow Response High to Low (Bank 1 Sensor 1)

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P22FA mirrors P22F9 for the falling edge: when engine-out NOx drops, mostly as the driver lifts off into overrun, the front NOx sensor on bank 1 takes too long to come down. GM's 2014 Cruze 2.0 diesel fails it when the signal needs more than 1.8 s between 30 and 60 % of its starting value at 1320 rpm or more; the 6.6L LML allows 2.3 s for a drop from 70 to 40 %. GM's 2016 diesel table uses a short timer above 4 s or a long one above 8 s, Type B. Software was often the real cause: GM PI1485 reflashed 2015 Cruze diesels that showed P22FA alongside a dashboard warning about poor DEF quality, and FCA flashed the 3.0L diesel of the 2014 ProMaster (18-018-15) and the 2020 Ram 1500 (18-008-21, 18-002-23). The MIL comes on.

Likely causes

Engine software anomaly, cured by reprogramming (GM PI1485, FCA 18-018-15, 18-008-21)
Front NOx sensor aged or contaminated, signal decays slowly
Exhaust leak near the sensor disturbing the measurement

Symptoms

  • Check engine light on
  • Warning about poor DEF quality on some GM diesels
  • Usually no change in engine behaviour

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

P22F9P22FBP22FDP2201P20EE

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