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.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: hard
Common causes
Ordered by how often each turns out to be the cause.
- Solenoid stuck closed by oil sludgeCommon
- Carbon or debris buildup preventing free movementLess likely
- Component wear with age - mechanical playLess likely
Parts involved
- Piston Cooling Solenoid
P25AC is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.