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

P25F6

AIR System B

A general fault in the second secondary air injection (AIR) circuit. Detected by the O2 sensors which expect a lean swing during cold-start AIR pump operation but do not see one.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number5 / F6

Possible causes

  • Failed AIR pump motor or impeller high
  • Check valve seized by exhaust soot medium
  • Corroded or cracked air injection pipe 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 pipes
  • 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