P2209
NOx Sensor Heater Sense Circuit Range/Performance (Bank 2)
The heater feedback (sense) line on the bank 2 NOx sensor reports values outside the expected window — heating is happening but the temperature does not match the model.
- 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 ageing, resistance driftCommon
- Sensor module failedPossible
- Sensor element aged beyond calibration windowLess likely
Parts involved
- NOX Sensor B2
- NOX Sensor Heater
P2209 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.