Powertrain
generic / SAE
P209E
Reductant Injection Air Pressure Sensor A/B Correlation
The two reductant injection air-pressure sensors A and B disagree by more than the allowed tolerance — one is reading off, or there is a real pressure imbalance between the two air-assist branches.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number– / 9E
Possible causes
- One sensor drifts relative to the other high
- Real imbalance between air branches 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: 80–600 €
- Estimated time: 0.7–2.5 h
- Component: reductant air pressure sensor
- Component: reductant air pump
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012