Failed oil pressure sensor or switch, the most common cause; Damaged, corroded, or disconnected electrical connector at the sensor; Open or shorted wire in the signal or reference circuit between the sensor and the control module; Poor ground connection for the sensor or the engine block; Contaminated or sludged engine oil blocking the sensor port and skewing the reading; Internal fault in the engine control module, rare but possible after other causes are ruled out

DTC codes / P05xx · Vehicle speed, idle control and auxiliary inputs / P0520

P0520Engine Oil Pressure Sensor/Switch Circuit Malfunction

Q: What does code P0520 mean?

Engine Oil Pressure Sensor/Switch Circuit Malfunction. P0520 means the engine control module has detected an abnormal signal on the circuit that connects it to the engine oil pressure sensor or switch, so it cannot trust the oil pressure reading. The computer is not directly measuring low oil pressure; it is flagging an electrical fault in the sensor, its wiring, or the circuit that feeds it.

P0520 means the engine control module has detected an abnormal signal on the circuit that connects it to the engine oil pressure sensor or switch, so it cannot trust the oil pressure reading. The computer is not directly measuring low oil pressure; it is flagging an electrical fault in the sensor, its wiring, or the circuit that feeds it.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Oil pressure warning lamp or message on the dashboard, sometimes intermittently
A gauge that reads zero, pegs high, or moves erratically if the vehicle has a real oil pressure gauge
Reduced engine power or a limp mode on some vehicles as a protective strategy
Rough running or stalling only if the fault is combined with an actual loss of oil pressure

Common causes, most likely first

Failed oil pressure sensor or switch, the most common cause
Damaged, corroded, or disconnected electrical connector at the sensor
Open or shorted wire in the signal or reference circuit between the sensor and the control module
Poor ground connection for the sensor or the engine block
Contaminated or sludged engine oil blocking the sensor port and skewing the reading
Internal fault in the engine control module, rare but possible after other causes are ruled out

How to diagnose and fix it

Check engine oil level and condition first, then verify the oil pressure sensor connector is fully seated and free of corrosion
Inspect the sensor wiring harness for chafing, broken strands, or heat damage along its routing
Use a scan tool to read live oil pressure sensor data and compare it with a mechanical oil pressure gauge reading
Test the sensor circuit with a multimeter for reference voltage, ground continuity, and signal return
Replace the oil pressure sensor or switch if the circuit tests good but the signal remains implausible
Clear the code and perform a road test to confirm the repair, then recheck for pending codes

What the oil pressure code really flags

P0520 is an electrical circuit code, so a perfectly healthy engine with good oil pressure can set it purely from a bad connector or chafed wire.
A mechanical oil pressure gauge test is the only way to prove whether the engine actually has low oil pressure or the sensor circuit is lying.
Sludge or debris blocking the sensor port can mimic a failed sensor, so the port should be checked before condemning the part.
Some vehicles use the same circuit for both a switch and a gauge, and a mismatch between the dash gauge and scan tool data points to a wiring fault rather than the sensor itself.
After replacing the sensor, the code may remain stored until several clean drive cycles complete, so do not assume the new part failed.

Can I keep driving with P0520?

It is usually safe to drive a short distance to a repair shop if the oil level is correct and there are no unusual engine noises, but avoid hard acceleration and long trips. Stop driving immediately if the oil pressure warning lamp comes on solid or the engine starts knocking, because that indicates a real loss of oil pressure.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.