OBD-II code · Powertrain (generic, extended)
P22FF SCR NOx Catalyst Inlet Temperature Too Low
The temperature sensor at the SCR catalyst inlet reports a value below the threshold needed for efficient ammonia conversion. Below roughly 180-200 °C the SCR cannot reduce NOx and reductant injection is suspended; if this is detected continuously the ECU sets the fault.
Is it safe to drive with P22FF?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyTemperature sensor drifts low or has shifted resistance
- PossibleShort-trip operation - exhaust never reaches operating temperature
- Less likelyExhaust heater or heat-management strategy not active
Symptoms
- Check engine light on
- Failed emissions inspection
- Possibly slightly increased fuel consumption
- Sulfur (rotten egg) smell from exhaust under load
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.8–1.6 h
- Emissions test
- Likely to fail
- Parts involved
- Scr Inlet Temperature Sensor, Scr Catalyst, Exhaust Heat Management
Related codes
- P22FCNOx Sensor Performance - Slow Response Low to High (Bank 1 Sensor 2)
- P22FDNOx Sensor Performance Slow Response High to Low Bank 1 Sensor 2
- P22FENOx Sensor Sensing Element Bank 1 Sensor 2
- P2300Ignition Coil A Primary Control Circuit Low
- P2301Ignition Coil A Primary Control Circuit High
- P2302Ignition Coil A Secondary Circuit
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.