Faulty oil pressure sensor or switch (45% likelihood): The oil pressure sending unit has failed internally, producing an incorrect or no signal. These sensors are inexpensive and commonly fail with age and heat exposure. Wiring or connector issue in sensor circuit (25% likelihood): Corroded, loose, or damaged wiring between the oil pressure sensor and the PCM/gauge causes the circuit to read incorrectly. Low engine oil level (15% likelihood): Insufficient oil in the engine results in genuinely low oil pressure, which the sensor is correctly reporting. Oil contamination or incorrect viscosity (10% likelihood): Degraded oil, fuel dilution, or using the wrong viscosity oil can cause actual oil pressure to fall outside the expected range. Failing oil pump (5% likelihood): A worn or failing oil pump cannot maintain adequate oil pressure, and the sensor is correctly detecting the low-pressure condition.

How much does it cost to fix P0520?

DIY repair typically costs $10–$40 for parts. Professional repair runs $80–$250 including parts and labor.

P0520

Powertrain

Moderate

Engine Oil Pressure Sensor/Switch Circuit

Get Your FREE AI Diagnostic Report

Enter your vehicle for a personalized diagnosis for code P0520

The P0520 code indicates a general malfunction in the engine oil pressure sensor or switch circuit. The PCM monitors the oil pressure sensor to ensure the engine has adequate lubrication. When the circuit produces a reading that is outside expected parameters — such as an open circuit, short, or implausible value — this code is stored.

The most visible symptom is usually an oil pressure warning light that stays on or an oil pressure gauge that reads abnormally. It's critical to understand that this code could indicate either a sensor/wiring problem or a genuine oil pressure issue. If the engine sounds normal with no ticking, knocking, or unusual noises, a sensor or wiring fault is more likely. However, if you hear any unusual engine sounds, treat this as an emergency.

Before assuming it's just a bad sensor, always verify the basics: check your oil level on the dipstick and make sure you're not overdue for an oil change. If the oil level is good and the engine sounds normal, replacing the oil pressure sensor is the most common fix — it's typically a $10-$40 part that screws into the engine block. For peace of mind, a mechanic can verify actual oil pressure with a mechanical gauge. Never ignore an oil pressure warning, as running an engine without adequate oil pressure can cause catastrophic damage within minutes.

Severity

High — Immediate AttentionWithin 24 Hours

Symptoms

•Oil pressure warning light on the dashboard stays on or flickers
•Oil pressure gauge reads zero, maximum, or fluctuates erratically
•Check Engine light is illuminated
•No noticeable change in engine performance in most cases
•Possible engine ticking or knocking if actual oil pressure is low

Likely Causes

Faulty oil pressure sensor or switch45%

The oil pressure sending unit has failed internally, producing an incorrect or no signal. These sensors are inexpensive and commonly fail with age and heat exposure.

Wiring or connector issue in sensor circuit25%

Corroded, loose, or damaged wiring between the oil pressure sensor and the PCM/gauge causes the circuit to read incorrectly.

Low engine oil level15%

Insufficient oil in the engine results in genuinely low oil pressure, which the sensor is correctly reporting.

Oil contamination or incorrect viscosity10%

Degraded oil, fuel dilution, or using the wrong viscosity oil can cause actual oil pressure to fall outside the expected range.

Failing oil pump5%

A worn or failing oil pump cannot maintain adequate oil pressure, and the sensor is correctly detecting the low-pressure condition.