Powertrain
generic / SAE
P20B2
Reductant Heater Coolant Control Valve Performance/Stuck Open
Reductant coolant control valve is electrically OK but stuck open or does not modulate as commanded — DEF heating loop loses control authority.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number– / B2
Possible causes
- Valve stuck open high
- Carbon or debris buildup preventing free movement low
- Component wear with age - mechanical play 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: 100–700 €
- Estimated time: 0.7–2.5 h
- Component: reductant coolant valve
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012