P22FA code meaning
NOx Sensor Performance - Slow Response High to Low (Bank 1 Sensor 1)
Powertrain system Generic code P22xx codes Check engine light
What P22FA means
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.
P22FA 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 P22FA
- Check engine light on
- Warning about poor DEF quality on some GM diesels
- Usually no change in engine behaviour
Common causes of P22FA
- Most likelyEngine software anomaly, cured by reprogramming (GM PI1485, FCA 18-018-15, 18-008-21)
- PossibleFront NOx sensor aged or contaminated, signal decays slowly
- Less likelyExhaust leak near the sensor disturbing the measurement
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 P22FA 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). |
| FA | The exact fault in that area. |
What to do next
- Note P22FA 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 P22FA
What does P22FA mean?
P22FA means "NOx Sensor Performance - Slow Response High to Low (Bank 1 Sensor 1)". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P22FA?
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 P22FA fail an emissions test?
Yes, it can. P22FA 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 P22FA to fix?
Difficulty: medium. A typical repair takes 0.3 to 2 hours of work. This is a job for a workshop.
Will P22FA 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.