Powertrain
Definition only
Lights the check engine lamp
P205B: Reductant Tank Temperature Sensor A Circuit Range/Performance
Standardized SAE J2012 code · P20xx — Fuel & air metering and auxiliary emission controls
What does P205B mean?
DEF tank temperature sensor A reads within electrical range but plausibility fails — sensor sticks during a heating cycle.
The code tells you which monitor failed, not which part is broken. Test before replacing parts.
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
- High Sensor drifts
- Low Sensor element aged beyond calibration window
- Low Sensor mounting loose - signal damping
Likelihood is a general estimate across vehicles; your make and model may differ.
Add your car to see reports of P205B on the same make and model first.
P205B in the community
Ask about P205BNo one has posted about P205B yet
Share your vehicle, the tool you used and what you tested — the first thread helps everyone who searches for this code.
Describe your P205B problem