Powertrain, generic (extended)

P25F9 Turbocharger/Supercharger Bypass Valve C Control Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Control wire shorted to ground
Valve coil shorted internally
Output stage in the engine control module faulty

Symptoms

  • Check engine lamp on
  • Too little boost if the valve stays open
  • Surging or fluttering on lift-off if it stays shut

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–600
Time0.5–3 h

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

Parts involved

bypass valve cbypass solenoidwiring harness

Related codes

P25F8P25FAP25FBP0034P00C1

References: law.cornell.edu, ms-motorservice.com, saabwisonline.com.