OBD-II code · Powertrain (generic, extended)
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.
Is it safe to drive with P209E?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyOne sensor drifts relative to the other
- PossibleReal imbalance between air branches
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)
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.7–2.5 h
- Emissions test
- Likely to fail
- Parts involved
- Reductant Air Pressure Sensor, Reductant Air Pump
Related codes
- P209BReductant Injection Air Pressure Sensor B Circuit Range/Performance
- P209CReductant Injection Air Pressure Sensor B Circuit Low
- P209DReductant Injection Air Pressure Sensor B Circuit High
- P209FReductant Tank Heater Control Circuit Performance
- P20A0Reductant Purge Control Valve A Circuit/Open
- P20A1Reductant Purge Control Valve A Performance
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.