P055F

What it means

P055F means the engine control unit has judged engine oil pressure to be out of its expected range for the current engine speed, load and oil temperature. The reading from the oil pressure sensor, or the pressure demanded from a controlled oil pump where fitted, was too low or too high for too long. The exact thresholds and the pump and sensor layout depend on the model and engine.

Symptoms

• Oil pressure warning light or engine warning light on
• Low oil pressure message or warning buzzer, especially at idle when hot
• Ticking, rattling or knocking from the engine
• Engine going into reduced power or limp mode on some models
• Erratic or implausible oil pressure gauge reading
• Possible rough running or poor response where oil pressure operates variable valve timing

Possible causes

• Engine oil level too low or too high, or oil heavily aged or diluted with fuellikely
• Wrong oil grade or viscosity for the enginelikely
• Faulty oil pressure sensor or switch giving an inaccurate readinglikely
• Wiring or connector fault on the sensor circuit, such as corrosion, chafing or poor earthpossible
• Blocked oil filter, blocked pickup strainer or sludge restricting oil flowpossible
• Worn oil pump, faulty pump control valve or stuck pressure relief valvepossible
• Internal engine wear, such as worn bearings, causing genuinely low pressurerare

How to diagnose

1. Read all stored and pending codes and the freeze frame data to see engine speed, load and oil temperature when the fault set, and note any related oil pressure sensor or valve timing codes.
2. Check the oil level on level ground with the engine off and settled, and inspect the oil for fuel smell, thinning, milkiness or heavy sludge.
3. Confirm the oil in the engine matches the manufacturer's specification for grade and approval, and check when it was last changed.
4. Inspect the oil pressure sensor, its connector and wiring for leaks, damage, corrosion and loose pins, and check the supply, signal and earth circuits against the model's wiring data.
5. View live oil pressure data, if the vehicle supports it, and compare it with the expected values at idle and raised engine speed, both cold and hot.
6. Fit a mechanical pressure gauge in place of the sensor to measure actual oil pressure and compare it with the sensor reading and the manufacturer's specification.
7. On engines with a controlled oil pump, test the pump control valve, its wiring and its commanded operation as per the model-specific procedure.
8. If real pressure is low and the oil and filter are fine, inspect the pump, pickup strainer and relief valve, and assess engine wear.

How to fix

• Correct the oil level and replace the oil and filter with the specified grade, and investigate and cure any fuel dilution.
• Repair or replace damaged wiring, connectors or earth connections on the oil pressure sensor circuit.
• Replace the oil pressure sensor if the mechanical gauge shows pressure is healthy but the sensor reading is wrong.
• Replace a faulty oil pump control valve, pressure relief valve or oil pump as the tests indicate.
• Clean or replace a blocked pickup strainer, after finding out why it clogged.
• Repair the engine internally if bearing or other wear is causing genuinely low oil pressure.

Can I keep driving?

Nearby codes

• P055EGenericOxygen Sensor Control Module System Voltage
• P0560GenericSystem Voltage