P22FCNOx Sensor Performance - Slow Response Low to High (Bank 1 Sensor 2)
- 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
- P22FC is reserved for the rear NOx sensor on bank 1, behind the SCR catalyst, when its signal climbs too slowly after NOx at that point increases. No manufacturer documents this code publicly, and the NHTSA bulletin index has no entry for it. GM, whose tables describe the front-sensor version P22F9, files the dynamic check of the rear sensor under P229F instead (2018 diesel fault bundle for the NOx2 dynamic test). CARB requires every NOx sensor to be watched for a loss of response rate before emissions pass the OBD limits (13 CCR 1968.2 (f)(5.2.2)(A)). Since a working SCR leaves little NOx downstream, a rising edge only shows during a dosing pause or a NOx burst. A slow outlet sensor can hide SCR faults; expect the MIL.
- What you may notice
- Check engine light on
- No change in driving behaviour
- Likely causes
- LikelyRear NOx sensor aged or contaminated by urea deposits, oil ash or cleaning agents
- RareExhaust leak between SCR catalyst and sensor
- RareCalibration of the test itself, check for software updates
- 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: €100 – €1,100
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.