P22C8Turbocharger Compressor Outlet Valve Stuck Open
- 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
- P22C8 is a functional fault: the compressor outlet valve stays open at a moment when the control strategy expects it shut, so pressure or airflow in the boost path does not follow the command. Mercedes-Benz uses it on the M256.8 inline six with its 48-volt electric auxiliary compressor. Bulletin LI09.41-P-078735 in its second version (March 2025) added P22C800 next to P22C900 for E, CLS, GLE and GLS 450, S 500/580 e and AMG 53 models and blames a jammed check valve in the charge-air pipe; the fix is a new charge-air line with integrated check valve. Listed symptoms are the warning lamp, weak output and faulty boost. Because the module must see the valve misbehave under suitable load, the code usually needs a test drive to confirm. P22C9 is the opposite case, a valve stuck shut.
- What you may notice
- Check engine light on
- Little or poor power output
- Boost builds poorly or unevenly
- Likely causes
- LikelyCheck valve in the charge-air pipe jammed (Mercedes M256)
- PossibleOil film or deposits holding the valve flap open
- RareActuator or linkage no longer able to close the valve
- 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.