P205B
Reductant Tank Temperature Sensor A Circuit Range/Performance
DEF tank temperature sensor A reads within electrical range but plausibility fails — sensor sticks during a heating cycle.
- 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.
- Sensor driftsCommon
- Sensor element aged beyond calibration windowLess likely
- Sensor mounting loose - signal dampingLess likely
Parts involved
- Reductant Tank Temperature Sensor
P205B 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.