OBD-II code · Powertrain (generic, extended)
P225F NOx Sensor Performance - Signal Biased/Stuck Low (Bank 1 Sensor 2)
The NOx sensor on bank 1 sensor 2 reads suspiciously low for too long — biased downward or stuck. Common after sensor element ageing, condensate damage from cold start, or wiring fault that pulls the signal down.
Is it safe to drive with P225F?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelySensor aged
- Less likelySensor element aged beyond calibration window
- Less likelySensor element contaminated by oil, soot or coolant
Symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1–3 h
- Emissions test
- Likely to fail
- Parts involved
- Nox Sensor
Related codes
- P225DNOx Sensor Performance - Signal Biased/Stuck Low (Bank 1 Sensor 1)
- P225CNOx Sensor Performance - Signal Biased/Stuck High (Bank 1 Sensor 1)
- P225ENOx Sensor Performance - Signal Biased/Stuck High (Bank 1 Sensor 2)
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Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.