Powertrain, generic (extended)

P25FC Turbocharger/Supercharger Bypass Valve C - Mechanical

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P25FC concerns the valve itself, not its wiring: bypass valve C is electrically in order but does not move as commanded, sticking open, shut or somewhere in between. A valve stuck open lets charge air leak back to the compressor inlet, so boost falls short; one stuck shut cannot relieve pressure when the throttle closes, and the compressor surges audibly. Which of the two cases the engine module can tell apart, and from which signals, is not published; no manufacturer documents valve C publicly, so the comparable codes P2261 (valve A) and P00C4 (valve B) are the closest reference. Deposits from crankcase vapours, a torn diaphragm or a cracked housing are typical. Electrical faults belong to P25F8–P25FB; a stuck valve C may also be reported as P2CD5.

Likely causes

Oil and soot deposits from crankcase ventilation jamming the valve
Torn diaphragm or broken spring inside the valve
Cracked valve housing or leaking seal

Symptoms

  • Check engine lamp on
  • Loud fluttering when lifting off the throttle
  • Lack of boost and power

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€100–800
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

bypass valve cactuator linkage

Related codes

P25FBP25FDP2CD5P2261P00C4

References: law.cornell.edu, ms-motorservice.com, en.wikipedia.org.