What it means
Control circuit stuck high — short to battery voltage or open coil/return. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
How it works
The piston-cooling oil control circuit operates the valve that directs engine oil to the piston cooling jets. The control module monitors the circuit’s electrical state and sets P25AB when it detects a high signal, such as a control wire shorted to battery voltage or an open coil or return path.
Common causes
Most likely first.
- Control wire shorted to battery voltage
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check-engine light may come on
- Piston-cooling function may be unavailable
- Engine may run hotter under heavy load
How to diagnose it
- Record freeze-frame data and check whether P25AB returns, since the conditions when the fault appears can help narrow down an intermittent wiring problem.
- Inspect the piston-cooling valve connector and harness for chafing, moisture, corrosion, loose pins, or a supply wire pinched against a battery-voltage source.
- With the code active, gently move the harness near the valve and connector while watching the circuit state on a scan tool for a change.
- Check the control wire for an unintended connection to battery voltage and inspect the supply and return paths for opens or poor connections.
- Test the valve coil and circuit continuity using the manufacturer's procedure and compare results with the manufacturer's specification.
Common fixes
- Repair chafed or pinched wiring that is shorting the control circuit to battery voltage.
- Clean or repair corroded connector terminals and correct any pushed-back pins.
- Restore an open supply or return connection.
- Replace the piston-cooling valve if its coil or internal connection fails testing.
Can I keep driving?
Avoid heavy loads and sustained high-speed driving because piston cooling may be unavailable and engine heat can rise. Stop if the engine overheats or an oil-pressure warning appears.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.