Powertrain, generic (extended)

P25AB Piston Cooling Oil Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P25AB is the counterpart on the supply side: the control line of the piston cooling oil valve is pulled toward battery voltage. In GM's 18OBDG04 diesel table the check runs while the low-side driver is switched on; if the output then looks tied to power through 0.5 ohm or less, the module counts a short to power, again needing 40 failed samples out of 50 at 100 ms intervals with at least 11 V and logging a Type B fault with the lamp after the second trip. A shorted driver normally switches itself off for protection, so the valve then gets no command at all. Deutz lists P25AB-12 when the valve feeding the piston jets on EMR L1 engines is shorted to battery. Owners mostly notice only the warning lamp; some engines cut power to spare the pistons.

Likely causes

Control wire pinched against a live supply wire
Valve side of the circuit shorted to its own supply
Damaged or contaminated valve connector
Faulty output stage in the engine control module

Symptoms

  • Check engine lamp after two drives
  • Piston cooling jets no longer switched
  • Possible reduced engine power

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

P25A9P25AAP25ACP25AD

References: gsi.ext.gm.com, serdia.deutz.com, law.cornell.edu.