P25A9Piston Cooling Oil Control Circuit/Open
- 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
- P25A9 covers the electrical circuit of the piston cooling oil control valve, the solenoid that switches the oil jets spraying the underside of the pistons. Under load the jets protect the pistons; when the engine is cold or lightly loaded they can be shut off to warm up faster and save oil pump work. GM's 2018 engine table 18OBDG04 checks the low-side driver of this valve on diesel engines while it is switched off and sets P25A9 when more than about 200 kilohm separate output and ground, meaning an open circuit, after 40 failures in 50 samples every 100 ms with at least 11 V supply (Type B, two trips); 17OBDG04 has the same check. Deutz EMR L1 engines log P25A9-13 for an open supply valve circuit and other subcodes for overcurrent or a shorted load. Stuck-off and stuck-on faults are P25AC and P25AD.
- What you may notice
- Check engine lamp on after two drives
- Possible power reduction to protect the pistons
- Likely causes
- LikelyPiston cooling valve coil open
- LikelyValve connector unplugged, corroded or wire broken
- PossibleHarness damaged by heat near the engine block
- RareOutput driver in the engine control module faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €80 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.