P2039Reductant Injection Air Pressure Sensor A Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P2039 is stored when the signal of injection air pressure sensor A sits below the lowest voltage a working sensor can deliver. Deutz documents it on its EMR L1 controller as P2039-00 under SPN 4335 and lumps two causes together: a grounded signal and an open circuit, since the input is pulled low when the signal wire is interrupted. A loss of the 5 V reference is another common reason for a reading near zero. Because the controller can no longer confirm that atomizing air is present, it stops DEF injection; Deutz engines then run without NOx reduction until the inducement logic of the machine steps in. The opposite fault is P2040, and electrical faults of the sensor supply fall under P2037.
- What you may notice
- Emission warning lamp on
- DEF injection stopped
- Power derate after a while on machines with inducement
- Likely causes
- LikelySignal wire open or shorted to ground
- Possible5 V reference to the sensor lost
- PossibleSensor output stuck low
- 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: €80 – €450
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.