P22C9Turbocharger Compressor Outlet Valve Stuck Closed
- 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
- P22C9 says the compressor outlet valve did not open when commanded, so air from the compressor it controls cannot reach the engine and the expected boost is missing. Mercedes-Benz documents the code for the M256.8 six-cylinder: the first version of bulletin LI09.41-P-078735 (December 2024) covers P22C900 in the MRG3 engine control unit on models from 2019 to 2025 and traces it to a check valve in the charge-air pipe that is jammed shut; the charge-air line with integrated check valve is replaced. Symptoms listed there are the engine lamp, reduced output and a boost malfunction. The check runs only under operating conditions that call for the valve to open, so confirmation usually takes a drive under load. Unlike P22C8, the risk here is a blocked path in which a compressor works against a closed outlet.
- What you may notice
- Check engine light on
- Noticeable loss of power under load
- Boost malfunction, possibly with underboost code
- Likely causes
- LikelyCheck valve in the charge-air pipe jammed shut (Mercedes M256)
- PossibleValve actuator, vacuum or pressure supply unable to open the valve
- RareValve seized by deposits or corrosion
- 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: €150 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.