P25AC code meaning
Piston Cooling Oil Control Circuit Performance/Stuck Off
Powertrain system Generic code P25xx codes Check engine light
What P25AC means
P25AC is a functional fault rather than a wiring one: the valve is told to let oil reach the piston jets, but the feedback shows no flow. GM's 18OBDG04 diesel table reads a pressure switch in the jet circuit and fails the test when that switch stays without pressure while the engine turns, main oil pressure is at least 206 kPa and the command has been held for 8 s or more; 40 of 50 samples must fail, Type B. Porsche technical information 2306 from March 2023 for the Macan four-cylinder from model year 2022 explains that P25AC00, displayed there as an implausible oil pressure switch signal, mostly stems from machining swarf jamming the control valve; a new valve, cleaning and an oil change cure it. Without cooling oil the pistons run hotter under load.
P25AC at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 4 hours
- Clears after repairAfter a drive cycle
Symptoms of P25AC
- Check engine lamp after two drives
- Engine power reduced under high load
- Risk of piston damage if driven hard for long periods
Common causes of P25AC
- Most likelyValve jammed by swarf or dirt in the oil
- PossiblePiston cooling pressure switch faulty or unplugged
- PossibleLow oil level or weak oil pressure feeding the jet circuit
- Less likelyRestricted oil passage to the jets
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 P25AC 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. |
| AC | The exact fault in that area. |
What to do next
- Note P25AC 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 P25AC
What does P25AC mean?
P25AC means "Piston Cooling Oil Control Circuit Performance/Stuck Off". P25AC is a functional fault rather than a wiring one: the valve is told to let oil reach the piston jets, but the feedback shows no flow. It is a generic code, so it means the same on every make.
Is it safe to drive with P25AC?
Drive gently and only to a workshop. With P25AC the car can go into limp mode (reduced power) to protect itself.
Will P25AC fail an emissions test?
Yes, it can. P25AC 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 P25AC to fix?
Difficulty: hard. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will P25AC 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.