Powertrain, generic (extended)

P25FA Turbocharger/Supercharger Bypass Valve C Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

With P25FA the control line of bypass valve C carries more voltage than the engine module expects for the commanded state. A wire shorted to battery voltage is the classic reason; on a ground-switched valve an open coil or broken lead also lets the line float up to supply level. A short to voltage can make the driver stage overheat and cut out, so the valve is no longer operated at all. On an electric recirculation valve, the effect is that it no longer opens on throttle lift-off and the compressor can surge, with the typical fluttering sound and some stress on the charger. No manufacturer documents P25FA for valve C; GM-based Saab engines monitor the same fault for valve A as part of a continuous type B circuit check. The low-side fault is P25F9.

Likely causes

Control wire shorted to battery voltage
Open valve coil on a ground-switched circuit
Damaged output stage in the engine control module

Symptoms

  • Check engine lamp on
  • Fluttering or surging noise when lifting off the throttle

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

P25F8P25F9P25FBP0035P00C2

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