Powertrain
generic / SAE
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.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number2 / FF
Possible causes
- Temperature sensor drifts low or has shifted resistance high
- Short-trip operation - exhaust never reaches operating temperature medium
- Exhaust heater or heat-management strategy not active low
Symptoms
- Check engine light on
- Failed emissions inspection
- Possibly slightly increased fuel consumption
- Sulfur (rotten egg) smell from exhaust under load
Inspection / repair
- Difficulty: medium
- DIY: shop recommended
- Estimated cost: 200–600 €
- Estimated time: 0.8–1.6 h
- Component: scr inlet temperature sensor
- Component: scr catalyst
- Component: exhaust heat management
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012