P209EReductant Injection Air Pressure Sensor A/B Correlation
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- When an air-assisted DEF system carries two air pressure sensors, the controller can compare them under conditions where both should read alike, for instance with the air supply shut and the lines vented to ambient, or at a steady dosing point. P209E is set when the two values stay apart by more than the calibrated margin even though each lies within its own electrical range. The code says nothing about which sensor is wrong; a slow drift of one, a restriction in only one branch or a leak between them all show up this way. The individual sensor faults are P2037 to P2041 for A and P209A to P209D for B. No manufacturer documents P209E publicly. CARB asks for such cross-checks wherever redundant inputs exist. The SCR system typically limits or stops dosing until the cause is found.
- What you may notice
- SCR or engine warning lamp on
- Live data shows clearly different values for sensors A and B at rest
- Reduced or suspended DEF dosing
- Likely causes
- LikelyOne of the two sensors drifted; compare both against a reference gauge
- PossibleRestriction or crystal build-up in only one air branch
- PossibleLeak in the air path between the two measuring points
- RareReplacement sensor with a different pressure range fitted
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €80 – €700
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.