What it means
The piston cooling solenoid does not close when commanded off — jets remain active when not needed. Oil pressure to top-end consumers may sag, and warm-up takes longer because the cooling jets remove heat from the pistons during cold start.
At a glance
- Usually lights the check-engine light
How it works
The piston-cooling oil control valve shuts off oil flow to the piston jets when cooling is not needed. P25AD sets when the control module commands the valve off but detects that it remains open, which can keep the jets flowing and divert oil from other engine areas.
Common causes
Most likely first.
- Solenoid stuck open
- Carbon or debris buildup preventing free movement
- Component wear with age - mechanical play
Symptoms
- Check-engine light may come on
- Oil-pressure warning light may appear
- Longer engine warm-up or reduced fuel economy
How to diagnose it
- Record freeze-frame data and check for oil-pressure, oil-temperature, or related control codes that may explain when the valve stayed on.
- Use scan-tool data to compare the piston-cooling command with its status and available oil-pressure feedback during warm-up.
- Inspect the valve connector and harness for damage or a control signal that remains active when the module commands the valve off.
- Check engine oil level and condition, then assess whether sludge or debris could be holding the valve open.
- Test the valve’s ability to close using the manufacturer's procedure and compare circuit and movement results with the manufacturer's specification.
Common fixes
- Repair wiring or connector faults that keep the valve commanded on.
- Clean or free a sticking piston-cooling valve if permitted by the manufacturer's procedure.
- Replace a valve that does not close when commanded off.
- Clear debris from the affected passage using the manufacturer's service procedure.
Can I keep driving?
If the oil-pressure warning appears, stop the engine as soon as it is safe and check the oil level; do not continue driving with a persistent warning. Otherwise, limit unnecessary trips because prolonged oil diversion can reduce pressure to other engine parts and slow warm-up.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.