P209BReductant Injection Air Pressure Sensor B Circuit Range/Performance
- 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
- Here the wiring of air pressure sensor B is intact and the voltage lies inside its valid band, yet the reported pressure makes no sense for the moment. Typical checks compare the value with the switching state of the air supply: pressure must rise when air is released to the mixing chamber and fall back when it is shut off, and with the system at rest it should sit near ambient. A sensor that sticks, drifts or reacts too slowly fails these tests. No manufacturer publishes P209B; Deutz reports such plausibility errors on its single air pressure sensor with its own code P1119. Besides the sensor, a leaking air line, a sticking supply valve or a clogged sensing port can produce the same picture. CARB requires rationality checks for every input the dosing strategy relies on.
- What you may notice
- Check engine or SCR warning lamp
- Dosing reduced or stopped, possible NOx efficiency codes later
- No noticeable change in driving until an inducement starts
- Likely causes
- LikelySensor B drifting or responding sluggishly
- PossibleLeak in the atomizing air line between valve and dosing module
- PossibleSensing port blocked by urea crystals or dirt
- RareAir supply valve sticking, so the expected pressure change does not occur
- 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 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.