Reductant Heater "A" Control Stuck On
The reductant tank heater "A" stays energised even when not commanded — usually a shorted driver stage. Continuous heating wastes current and can overheat the heater element.
Affected components
- Reductant tank heater
- Reductant dosing unit
Common causes
- High likelihood: Heater driver shorted on
- Medium likelihood: Heater line shorted to positive
- Low likelihood: Carbon or debris buildup preventing free movement
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
- A drive cycle may be required after repair
Related codes
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.