P25AD code meaning
Piston Cooling Oil Control Circuit Stuck On
Powertrain system Generic code P25xx codes Check engine light
What P25AD means
P25AD describes the reverse mechanical failure: the piston cooling valve ought to be shut, yet oil keeps reaching the jets. GM's diesel table 18OBDG04 detects it when the pressure switch in the jet circuit reports pressure although the valve has been commanded to its off state for at least 8 s, with the engine turning and main oil pressure of at least 206 kPa; 40 bad samples out of 50 make it a Type B fault. Dirt or a broken return spring holding the valve open is the usual reason, a switch stuck closed the rarer one. The pistons are not at risk, but the jets bleed oil constantly, which can lower pressure at other consumers and lengthens warm-up after a cold start. Apart from GM, no manufacturer documents this code publicly.
P25AD at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyHard
- Typical labor1 to 4 hours
- Clears after repairAfter a drive cycle
Symptoms of P25AD
- Check engine lamp after two drives
- Longer warm-up in cold weather
- Slightly lower oil pressure reading at idle
Common causes of P25AD
- Most likelyValve held open by debris
- PossibleBroken return spring in the valve
- Less likelyPiston cooling pressure switch stuck in the pressure position
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Piston cooling solenoid
What each part of P25AD means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| AD | The exact fault in that area. |
What to do next
- Note P25AD and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P25AD
What does P25AD mean?
P25AD means "Piston Cooling Oil Control Circuit Stuck On". P25AD describes the reverse mechanical failure: the piston cooling valve ought to be shut, yet oil keeps reaching the jets. It is a generic code, so it means the same on every make.
Is it safe to drive with P25AD?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P25AD fail an emissions test?
Yes, it can. P25AD is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P25AD to fix?
Difficulty: hard. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will P25AD clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.