P25ACPiston Cooling Oil Control Circuit Performance/Stuck Off
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- Check engine lamp after two drives
- Engine power reduced under high load
- Risk of piston damage if driven hard for long periods
- Likely causes
- 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
- RareRestricted oil passage to the jets
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €150 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.