P209DReductant Injection Air Pressure Sensor B Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- With P209D the second air pressure sensor reports a voltage above the top of its usable range, close to the supply or battery level. A real air pressure that high is not possible in the system, so the controller treats the value as an electrical fault. Usual explanations are a signal wire that touches a live conductor, a broken ground return so that the output floats up to the reference, or an open signal line on circuits that pull the input high. P209C is the mirror case with a reading too low, and P209A the umbrella code when the type of circuit fault cannot be narrowed down. P209D does not appear in any public manufacturer list; Deutz assigns the corresponding short to battery on sensor A to P2040. The SCR controller stops dosing because it can no longer confirm atomization, and the warning lamp comes on.
- What you may notice
- Warning lamp on, dosing stopped
- Displayed air pressure stays at an impossibly high value
- Inducement countdown on heavy vehicles if not repaired
- Likely causes
- LikelySensor ground open at the connector or splice
- PossibleSignal wire shorted to the 5 V reference or battery voltage
- PossibleSensor B output stage failed high
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €60 – €450
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.