Powertrain
generic / SAE
P20ED
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.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number– / ED
Possible causes
- Heater driver shorted on high
- Heater line shorted to positive medium
- Carbon or debris buildup preventing free movement low
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)
Inspection / repair
- Difficulty: medium
- DIY: shop recommended
- Estimated cost: 200–1200 €
- Estimated time: 1–4 h
- Component: reductant tank heater
- Component: reductant dosing unit
- MIL / check engine light
- emissions-relevant
- drive cycle required
Sources
References
sae:J2012