P2208
NOx Sensor Heater Circuit (Bank 2)
A general electrical fault on the heater of the bank 2 NOx sensor. NOx sensors must reach roughly 800 C to measure correctly; without heater current the sensor never enters its operating range.
- 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 failedCommon
- Heater wiring open or connector loosePossible
Parts involved
- NOX Sensor B2
- NOX Sensor Heater
P2208 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.