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

P25AC

Piston Cooling Oil Control Circuit Performance/Stuck Off

The control circuit is electrically intact, but the solenoid valve does not open when commanded — confirmed by oil-pressure or oil-temperature feedback that does not change after the activation pulse. Piston cooling does not engage under high load — risk of piston-crown overheating and ring-land cracks.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number5 / AC

Possible causes

  • Solenoid stuck closed by oil sludge high
  • Carbon or debris buildup preventing free movement low
  • Component wear with age - mechanical play low

Inspection / repair

  • Difficulty: hard
  • DIY: shop recommended
  • Estimated cost: 300–1500 €
  • Estimated time: 1.5–5 h
  • Component: piston cooling solenoid
  • 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