P25F9Turbocharger/Supercharger Bypass Valve C Control Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P25F9 tells that the control line of bypass valve C reads too low a voltage, normally because it touches ground somewhere or the coil is shorted. If the engine module switches the valve on the ground side, a grounded wire leaves the valve energised all the time; on an electric recirculation valve, which according to Pierburg works without a vacuum line, that means charge air keeps escaping back to the compressor inlet and boost stays short. If the valve is switched on the supply side, it simply stops opening and the compressor can surge when the throttle snaps shut. No manufacturer publishes P25F9; the Saab circuit check for valve A (10 s, type B) is the nearest documented analogue. The high-voltage counterpart is P25FA.
- What you may notice
- Check engine lamp on
- Too little boost if the valve stays open
- Surging or fluttering on lift-off if it stays shut
- Likely causes
- LikelyControl wire shorted to ground
- PossibleValve coil shorted internally
- RareOutput stage in the engine control module faulty
- 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 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.