P00C4Turbocharger/Supercharger Bypass Valve B - Mechanical
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- Bypass valve B is the compressor recirculation (diverter) valve of turbocharger B, not the wastegate: it lets charge air flow back to the compressor inlet when the throttle closes quickly, so the compressor does not surge. Turbocharger B is the second turbocharger in exhaust flow on series systems and the turbocharger of bank 2 on parallel twin-turbo engines. P00C4 reports that the valve stays mechanically closed. A documented method detects this on overrun from the pulsation of the measured air mass that compressor surge causes when the valve should open.
- What you may notice
- Check engine light on
- Fluttering or surging noise when lifting off the throttle
- Boost fluctuations, loss of power
- Likely causes
- LikelyValve stuck closed or coked
- PossibleDiaphragm or piston worn
- PossibleValve not actuated correctly
- RareConsequence of a boost or air flow fault
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €60 – €350
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.