Powertrain
generic / SAE
P20A4
Reductant Purge Control Valve A Stuck Open
Reductant purge control valve A is mechanically stuck open — system cannot maintain dosing pressure because the line is constantly vented to the tank.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number– / A4
Possible causes
- Valve stuck open mechanically 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: 120–800 €
- Estimated time: 0.7–3 h
- Component: reductant purge valve
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012