Powertrain, generic (extended)

P25A9 Piston Cooling Oil Control Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

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.

Likely causes

Piston cooling valve coil open
Valve connector unplugged, corroded or wire broken
Harness damaged by heat near the engine block
Output driver in the engine control module faulty

Symptoms

  • Check engine lamp on after two drives
  • Possible power reduction to protect the pistons

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–600
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

piston cooling solenoidwiring harness

Related codes

P25AAP25ABP25ACP25AD

References: gsi.ext.gm.com, serdia.deutz.com, gsi.ext.gm.com.