P25AC

Code

Generic P — Powertrain

Piston Cooling Oil Control Circuit Performance/Stuck Off

Brand: Generic

Type: P — Powertrain

Views: UK: 29 EN: 153 RU: 33

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Page language: EN

Causes

Open or short in solenoid/control wiring
Faulty piston cooling oil control solenoid/actuator (stuck or failed)
Corroded or loose connector at the solenoid
Clogged oil passage, nozzle, or filter for piston cooling jets
Low engine oil level, incorrect oil viscosity, or degraded oil pressure
ECM/PCM software or internal fault

Symptoms

MIL (check engine light) illuminated and code P25AC stored
No audible click from the piston cooling oil solenoid when commanded
Reduced or no oil spray to piston underside under load (may cause increased piston/top-ring temperatures over time)
Possible oil pressure-related warnings if oil level/pressure is low
Driveability may be unaffected immediately but long-term engine wear risk increases

What to check

Read and record freeze frame and related stored codes; check for pending or multiple occurrences
Visually inspect solenoid connector and wiring for corrosion, damage, or loose pins
Check engine oil level and condition; verify correct oil grade used
Attempt to command the piston cooling oil control ON/OFF using a scan tool and observe system response
Listen at the solenoid for an audible click when commanded ON/ OFF
Check for additional DTCs related to oil pressure, ECM power/ground, or cam/crank sensors

Signal parameters

Control supply voltage: nominal battery voltage (~12 V) at Harness/ECM supply when key ON
Control signal type: typically driven by ECM as switched 12 V or PWM — expected control duty 0–100% depending on command
Solenoid coil resistance (typical range): generally low (approx. 5–30 ohms) — varies by manufacturer; compare to spec
Control circuit current when activated: typically under 2–3 A for most solenoids; excessive current suggests short/lock, very low suggests open circuit
Expected feedback: when commanded ON the solenoid coil should show continuity and voltage; when commanded OFF it should show no drive voltage

Diagnostic algorithm

Retrieve freeze frame and related codes; note engine conditions when code set (temp, rpm, oil temp/pressure if available).
Perform visual inspection: battery condition, fuses/relays related to oil control system, ECM grounds and power feeds. Repair any obvious damage.
Verify oil level and condition; top up with correct viscosity oil if low. Replace oil if contamination or wrong grade suspected.
Using a scan tool, command the piston cooling oil control ON and OFF while monitoring control voltage at the solenoid connector. Observe for voltage presence and duty-cycle changes. Record results.
If no voltage is present when commanded, backprobe the harness at the ECM connector and check for open/short to ground or battery. Repair wiring as needed.
If correct voltage is present but solenoid does not respond, disconnect connector and measure solenoid coil resistance. If open or out of expected range for vehicle, replace solenoid.
Bench-test solenoid: apply appropriate battery voltage (observe polarity and duty if required by design) briefly to confirm mechanical operation and audible click. Use caution and short pulses to avoid damage. Replace if stuck or non-responsive.
If solenoid operates electrically but no oil flow occurs, inspect oil feed line, nozzle, and filter for clogging or restrictions. Clean or replace components as required.
Check engine oil pressure with a mechanical gauge at idle and load to ensure sufficient system pressure. Low mechanical oil pressure must be repaired and retested.
Inspect and repair any corroded/loose connectors or damaged harness sections. Use proper crimping/soldering and dielectric grease as appropriate.
After repairs, clear codes and perform a road/drive cycle under the conditions that previously set the code. Re-scan to confirm code does not return. If intermittent, consider wiring harness replacement or ECM diagnostics.

Likely causes

Failed piston cooling oil control solenoid (electromechanical stuck closed or open)
Broken or corroded harness connector pin to the solenoid
Clogged cooling oil nozzle or restriction in the oil feed line
Open circuit or high resistance in the control circuit
Low oil pressure preventing flow even when solenoid is commanded open

Fault status

⚠️ Status

Malfunction Indicator Lamp (MIL) may be illuminated. Code indicates piston cooling oil control circuit performance issue or stuck OFF; engine may disable or not provide piston cooling oil flow when commanded. Stored as active/fault until repaired and verified.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours