OBD-II reference

All 9.533 generic OBD-II codes, explained in detail.

Causes, inspection steps and sources — a comprehensive DIY archive. Created and maintained with love for the detail. Good luck and have fun!

Powertrain generic / SAE

P25FC

Turbocharger/Supercharger Bypass Valve C - Mechanical

The third bypass valve is mechanically jammed. Solenoid is energised correctly but the valve flap or disc does not move as expected.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number5 / FC

Possible causes

  • Carbon buildup blocks the valve flap high
  • Actuator linkage seized by corrosion medium

Symptoms

  • Check engine light on
  • Significant power loss / limp mode
  • Possible blue or black smoke from exhaust
  • Whistling or hissing sound from intake

Inspection / repair

  • Difficulty: hard
  • DIY: shop recommended
  • Estimated cost: 200–1500 €
  • Estimated time: 1.5–5 h
  • Component: bypass valve c
  • Component: actuator linkage
  • MIL / check engine light

Sources

References

How to read OBD-II codes

The first letter names the vehicle system, the second digit distinguishes generic from manufacturer-specific, the remaining digits group fault area and number.

PPowertrain: engine, transmission, emissions
BBody: chassis trim, comfort, interior
CChassis: suspension, brakes, steering
UNetwork: CAN, control modules, communication