P20A9Reductant Injection Air Pressure Control Valve 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
- If the control line of the air pressure control valve shows battery voltage or excessive current where it should not, P20A9 is stored. A wire touching a positive feed, a coil with shorted turns or a bridged connector can cause it. On a low-side driven valve the coil would then be live permanently; on a high-side driver the output often detects overcurrent and shuts down. Either way the atomizing air no longer follows the commands. P20A8 is the matching short to ground and P20A6 the open circuit. No manufacturer publishes P20A9. Deutz handles the comparable faults on its air pump or supply valve as P2061 for a short to battery and P2059-19 for critically high output current. Because the air supply is shared, check for further codes on the air pressure sensors before replacing parts.
- What you may notice
- Warning lamp on
- Air pressure uncontrolled, often too high or permanently on
- DEF dosing suspended
- Likely causes
- LikelyCoil with shorted turns causing overcurrent
- PossibleControl wire shorted to a positive feed in the harness
- RareOutput stage in the dosing control unit defective
- 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: €50 – €500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.