Reductant Temperature Too High
The temperature of the AdBlue/DEF in the dosing system exceeds the safe limit — risk of thermal decomposition (NH3/biuret formation) and clogged dosing nozzles. Often caused by a stuck-on tank heater, a stalled coolant return or proximity to a hot exhaust component.
Affected components
- Reductant tank
- Reductant tank heater
- Reductant lines
Common causes
- High likelihood: Tank heater stuck on
- Medium likelihood: Heat soak from exhaust or engine bay
Possible 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)
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.