Powertrain
generic / SAE
P20AA
Reductant Injection Air Pressure Control Valve Stuck Open
Reductant air-pressure control valve mechanically stuck open — air pressure cannot be reduced, dosing atomisation off-spec.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number– / AA
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: 120–800 €
- Estimated time: 0.7–3 h
- Component: reductant air pressure control valve
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012