P055C
Engine Oil Pressure Sensor/Switch B Low.
- Generic
- Powertrain
- Generic code
- High severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 5
- AreaVehicle speed, idle control and auxiliary inputs
- 5C
- FaultThe specific fault in that area
What it means
P055C is a generic code meaning the engine control unit has seen a low signal from engine oil pressure sensor or switch 'B'. The signal voltage or state is below the expected range for the operating conditions, which may be a genuine oil pressure problem or a fault in the sensor or its circuit. Which sensor is 'B' and how the fault is judged depends on the make, model and engine.
Symptoms
- Oil pressure warning light on the dashboard
- Warning message or buzzer on the instrument cluster
- Engine management light on
- Oil pressure gauge reading low, erratic or zero
- Engine noise such as ticking or rattling if pressure is genuinely low
- Reduced engine power or limp mode on some vehicles
Possible causes
- Genuinely low oil pressure from low oil level or degraded, diluted or wrong-grade oillikely
- Faulty oil pressure sensor or switch B giving a false low readinglikely
- Damaged wiring, poor connection or corroded terminals in the sensor signal, supply or earth circuit (short to earth or high resistance)likely
- Oil leak or oil contaminated sensor connectorpossible
- Blocked oil filter, blocked pickup strainer or failing oil pump, or relief valve stuck openpossible
- Worn engine bearings causing true loss of oil pressurerare
- Fault in the engine control unit's sensor input or supplyrare
How to diagnose
- Read all stored codes and freeze frame data, noting engine speed, temperature and load when the fault set, and check for other oil pressure or sensor supply codes.
- Check the oil level on level ground and inspect the oil condition, looking for fuel or coolant dilution and confirming the correct grade and specification.
- Inspect the sensor, connector and wiring for oil soaking, chafing, corrosion, bent pins or leaks around the sensor.
- Check the live oil pressure sensor data against expected values at cold start, idle and higher revs, if the vehicle supports it.
- Check the sensor supply voltage, signal and earth with a multimeter, following the manufacturer wiring diagram for your model.
- Fit a mechanical oil pressure gauge in place of the sensor to compare actual pressure with the specification and decide whether the fault is real or electrical.
- If actual pressure is low, check the oil filter, any pressure relief valve, pickup strainer and oil pump condition, as the procedure varies by engine.
- Clear the code after repair and road test to confirm it does not return.
How to fix
- Correct the oil level and change oil and filter to the correct specification if the oil is degraded or diluted, and fix the cause of any dilution.
- Replace the oil pressure sensor or switch if it is faulty or fails testing.
- Repair or replace damaged wiring, connectors or terminals in the sensor circuit.
- Fix any oil leaks and clean or replace the oil-contaminated connector.
- Replace a blocked filter, clean or replace the pickup strainer, or repair the oil pump or relief valve as the pressure test indicates.
- Carry out engine mechanical repair if worn bearings or internal wear are confirmed.
Can I keep driving?
Do not keep driving if the oil pressure warning light is on or the oil level is low, as genuine low oil pressure can quickly destroy the engine. Stop safely, check the oil level and get the car checked before further use, with the pressure confirmed as normal before it returns to regular driving.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.