P25AD

Code

Generic P — Powertrain

Piston Cooling Oil Control Circuit Stuck On

Brand: Generic

Type: P — Powertrain

Views: UK: 25 EN: 49 RU: 22

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Causes

Short to battery (power) in the piston cooling oil control circuit
Failed piston cooling oil control solenoid or valve mechanically stuck closed
Corroded, damaged, or bridged connector pins or wiring harness
PCM/output driver stuck ON or internal failure
Relays or fuses supplying the circuit stuck or welded closed
Aftermarket wiring or poor repairs creating an unintended feed

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Stored P25AD fault and possible reduced engine performance or limp mode depending on calibration
Uncommanded piston cooling oil flow (could affect oil pressure or oil temperature)
Related oil pressure or temperature warnings in some vehicles

What to check

Read and record all stored codes and freeze-frame data with a scan tool. Check for related oil pressure/temperature or control circuit codes.
Compare PCM command (requested state) vs actual feedback (if available) using scan tool PIDs while toggling the control.
Visual inspection of connector, wiring, and solenoid for damage, corrosion, melted insulation, or fluid contamination.
Backprobe the solenoid connector and check for battery voltage with ignition ON and with PCM commanding OFF.
Measure solenoid coil resistance with connector disconnected and battery off; compare to specification.
Use a scope or DVOM to check for PWM or steady voltage at the solenoid while commanding ON and OFF.

Signal parameters

Rest (OFF) state: no PWM; ideally ~0 V at solenoid coil (if ground-switched) or battery voltage removed (if supply-switched)
Active (ON) state: PWM or steady 12 V depending on design. PWM frequency commonly in the 20–200 Hz range on many systems (manufacturer-specific).
Typical coil resistance: often in the low ohms range (e.g., 2–40 Ω); compare with OEM spec for the specific solenoid.
Current draw when ON: generally below several amps; excessive current suggests short or stuck valve.
Scan-tool PID: Commanded = OFF while Feedback = ON indicates stuck-on condition

Diagnostic algorithm

Use a scan tool to record DTCs, Freeze Frame and live data (command vs feedback). Clear codes and re-run to confirm repeatability.
Perform a visual inspection of the solenoid, connector, and harness. Look for melting, chafing, oil ingress, or previous repairs.
With ignition OFF and battery disconnected, disconnect the sensor/solenoid connector and measure coil resistance across the solenoid terminals. Compare to spec.
Reconnect battery, backprobe the solenoid connector. With ignition ON and PCM commanding OFF, check for battery voltage at the connector. Presence of voltage indicates a short to power or stuck driver.
Command the solenoid ON and OFF using the scan tool while monitoring voltage/current or using an oscilloscope to observe PWM and state changes. Verify ECU command changes but the actual circuit remains ON when commanded OFF.
If the solenoid is not energized when commanded ON with the connector disconnected, suspect open harness. If the circuit remains energized with the connector disconnected, suspect PCM or an upstream power feed/relay.
Inspect and test fuses and relays that feed the circuit for welds or stuck contacts. Remove any suspected relay and re-test.
Repair any wiring harness faults, terminal corrosion, or shorted insulation found. After harness repair, retest to confirm normal operation.
If harness and solenoid test good but circuit is still driven when it should be off, consider replacing or repairing the PCM only after verifying all other causes and following manufacturer procedures (verify part numbers, reprogramming requirements).
After repair, clear codes, perform functional tests and a road test (or burn-in procedure) to confirm the fault does not return.