P22C8 code meaning
Turbocharger Compressor Outlet Valve Stuck Open
Powertrain system Generic code P22xx codes Check engine light
What P22C8 means
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.
P22C8 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 2.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P22C8
- Check engine light on
- Little or poor power output
- Boost builds poorly or unevenly
Common causes of P22C8
- Most likelyCheck valve in the charge-air pipe jammed (Mercedes M256)
- PossibleOil film or deposits holding the valve flap open
- Less likelyActuator or linkage no longer able to close the valve
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Diverter valve
What each part of P22C8 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 2 | Area: fuel and air metering (injector circuit). |
| C8 | The exact fault in that area. |
What to do next
- Note P22C8 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P22C8
What does P22C8 mean?
P22C8 means "Turbocharger Compressor Outlet Valve Stuck Open". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P22C8?
Drive gently and only to a workshop. With P22C8 the car can go into limp mode (reduced power) to protect itself.
Will P22C8 fail an emissions test?
Yes, it can. P22C8 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P22C8 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. This is a job for a workshop.
Will P22C8 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.