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

P25F7

AIR System B Incorrect Flow Detected

The second AIR system delivers measurably more or less air than expected. Often a partially blocked pipe, a worn pump, or a leak between pump and check valve.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number5 / F7

Possible causes

  • Air pipe partially blocked by carbon high
  • Worn pump impeller reduces flow medium
  • Leak between pump and check valve medium

Inspection / repair

  • Difficulty: hard
  • DIY: shop recommended
  • Estimated cost: 200–1500 €
  • Estimated time: 1.5–5 h
  • Component: air pump b
  • Component: air check valve
  • Component: air flow sensor
  • MIL / check engine light
  • emissions-relevant

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