Powertrain
generic / SAE
P20E6
Reductant Injection Air Pressure Too Low
The DEF system air-assist pressure is below the required threshold — pump weak, line leak, or pressure-control valve stuck open.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number– / E6
Possible causes
- Air pump weak high
- Leak in air line medium
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: 120–900 €
- Estimated time: 0.7–3 h
- Component: reductant air pump
- Component: reductant air pressure control valve
- Component: reductant air line
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012