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

P25A9

Piston Cooling Oil Control Circuit/Open

The piston-cooling oil-jet control circuit is open. Modern engines with under-piston oil jets switch them on under high load to cool the piston crown — controlled by a solenoid valve in the oil gallery. With the circuit broken, jets cannot be commanded on or stay locked off, raising piston temperatures under load.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number5 / A9

Possible causes

  • Open control wire to the solenoid high
  • Open solenoid coil medium
  • Pin pushed back out of connector body low

Inspection / repair

  • Difficulty: hard
  • DIY: shop recommended
  • Estimated cost: 200–1200 €
  • Estimated time: 1–4 h
  • Component: piston cooling solenoid
  • Component: wiring harness
  • 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