Faulty oil pressure sensor or switch (internal failure or drift); Damaged, chafed or corroded wiring to the sensor, including short to earth, short to voltage or open circuit; Corroded, loose or oil-soaked connector at the sensor; Genuinely low or high oil pressure caused by low oil level, wrong oil grade, worn oil pump or worn bearings; Oil leaking past the sensor seal or along the harness, contaminating the connector; Poor earth connection or low supply voltage to the sensor; Fault within the engine control unit or instrument cluster circuit.

P0520

Engine Oil Pressure Sensor/Switch A Circuit.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
5: AreaVehicle speed, idle control and auxiliary inputs
20: FaultThe specific fault in that area

What it means

P0520 is the generic code for a fault in the engine oil pressure sensor or switch 'A' circuit. The engine control unit has seen a signal from the sensor or its wiring that is out of range, implausible or does not match engine speed and running conditions. It points to the sensing circuit being faulty, but it does not on its own prove that the oil pressure is actually low.

Symptoms

Oil pressure warning light on, flickering or staying off when it should light at key-on
Oil pressure gauge reading zero, erratic or stuck
Malfunction indicator lamp or a warning message on the dashboard
Intermittent warnings that come and go with engine temperature or speed
Engine protection or reduced power mode on some models
No noticeable change in how the engine runs

Possible causes

Faulty oil pressure sensor or switch (internal failure or drift)likely
Damaged, chafed or corroded wiring to the sensor, including short to earth, short to voltage or open circuitlikely
Corroded, loose or oil-soaked connector at the sensorlikely
Genuinely low or high oil pressure caused by low oil level, wrong oil grade, worn oil pump or worn bearingspossible
Oil leaking past the sensor seal or along the harness, contaminating the connectorpossible
Poor earth connection or low supply voltage to the sensorpossible
Fault within the engine control unit or instrument cluster circuitrare

How to diagnose

Check the engine oil level and condition on level ground, and top up or investigate if it is low, diluted or the wrong grade
Read the stored codes and freeze frame data, noting engine speed, temperature and whether other codes are present, then check for any related instrument cluster warnings
Inspect the sensor, its connector and the harness for oil contamination, chafing, heat damage, corrosion and a poor seal
Check the sensor for oil leakage and confirm it is fitted correctly and not damaged
With the ignition on, check the sensor's supply, signal and earth against the manufacturer's data for your model, as the sensor type (switch or analogue) and values vary
Wiggle-test the harness and connector while watching live data or the gauge for sudden changes in the reading
Check actual oil pressure with a mechanical gauge to confirm whether the engine pressure is within specification before replacing parts
Check the wiring for continuity and shorts between the sensor and control unit if the sensor and supply check out

How to fix

Replace the oil pressure sensor or switch with the correct type for the engine, using a new seal where fitted
Repair or replace damaged wiring and clean or renew corroded or oil-soaked connectors
Correct the oil level or change to the specified oil and filter if the oil is the cause
Repair real low oil pressure at its source, such as a worn oil pump, pressure relief fault or engine wear, as confirmed by a mechanical pressure test
Restore faulty earth or supply connections to the sensor circuit

Can I keep driving?

Medium severity

If the oil level is correct and the warning light behaves normally, short-term driving is usually possible but get it checked soon. If the oil light is on with the engine running, or you hear knocking or ticking, stop driving, because genuinely low oil pressure can quickly cause severe engine damage.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.