P22FC code meaning
NOx Sensor Performance - Slow Response Low to High (Bank 1 Sensor 2)
Powertrain system Generic code P22xx codes Check engine light
What P22FC means
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.
P22FC at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.3 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of P22FC
- Check engine light on
- No change in driving behaviour
Common causes of P22FC
- Most likelyRear NOx sensor aged or contaminated by urea deposits, oil ash or cleaning agents
- Less likelyExhaust leak between SCR catalyst and sensor
- Less likelyCalibration of the test itself, check for software updates
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Nox sensor
What each part of P22FC means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 2 | Area: fuel and air metering (injector circuit). |
| FC | The exact fault in that area. |
What to do next
- Note P22FC and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P22FC
What does P22FC mean?
P22FC means "NOx Sensor Performance - Slow Response Low to High (Bank 1 Sensor 2)". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P22FC?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P22FC fail an emissions test?
Yes, it can. P22FC is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P22FC to fix?
Difficulty: medium. A typical repair takes 0.3 to 2 hours of work. This is a job for a workshop.
Will P22FC clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.