P224B
NOx Sensor Heater Resistance (Bank 1 Sensor 2)
The measured heater element resistance of the NOx sensor on bank 1 sensor 2 is outside the calibrated range. Used as a sensor-element health check.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
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)
Common causes
Ordered by how often each turns out to be the cause.
- Heater element agedCommon
Parts involved
- NOX Sensor
P224B is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.