P0520 on Subaru: How to Diagnose & Fix
Engine Oil Pressure Sensor/Switch Circuit Malfunction
1 Subaru model · 1 documented issue · 1 critical · $200-$3,500 repair
P0520 on Subaru by model: symptoms, diagnosis and fix
The EJ257 boxer engine uses a shallow oil pan design that is prone to oil starvation during sustained high-G cornering, particularly on track days or aggressive canyon driving. The flat-four layout means oil sloshes away from the pickup tube during lateral loading, starving rod and main bearings of lubrication. This is a leading cause of spun rod bearings and catastrophic engine failure on STIs used for motorsport or spirited driving.
Common Symptoms
- Low oil pressure warning light during hard cornering
- Rod knock or bearing noise after track sessions
- Metal flakes in oil filter at oil change
- Sudden loss of oil pressure under lateral G-forces
- Engine failure after sustained aggressive driving
How to Fix
Install an aftermarket baffled oil pan or oil pan baffle kit ($200-$400) from vendors like Killer B Motorsport or Crawford Performance. An air-oil separator (AOS) also helps by returning oil vapor to the sump. For dedicated track cars, a dry sump conversion ($2,000-$3,500) eliminates the issue entirely. Always run a quality 5W-30 or 5W-40 oil and check level before every track session.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Killer B PPBC Cast Oil Pan, Ultimate Pickup and Baffle Package
matched track-use sump-control package after the vehicle use and oil-pressure evidence justify the modification Fitment/availability: 2004-2021 STI EJ257; also cataloged for 2002-2014 WRX, confirm header clearance, oil capacity and dipst…
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Owner tips & cautions
- WarningIf you track your STI on the stock oil pan, you WILL eventually spin a bearing. This is not an if, it is a when. Budget for the baffle before your first track day.
Sources for this issue (1)
P0520 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0520 mean on a Subaru?
P0520 stands for "Engine Oil Pressure Sensor/Switch Circuit Malfunction." This code indicates a general electrical fault in the circuit for the engine oil pressure sensor or switch. The computer monitors this circuit to know your oil pressure, and it has detected a signal that is missing, shorted, or otherwise out of the expected electrical range. This is typically a wiring or sensor problem rather than an actual loss of oil pressure, but because oil pressure is critical to engine life, it should never be ignored until confirmed. If oil pressure truly is low, serious engine damage can result. On Subaru it is documented across 1 model: WRX STI.
What are the most common causes of P0520?
The most common causes of P0520 are: Faulty oil pressure sensor or switch, Damaged, corroded, or loose wiring/connector at the sensor, Open or short in the sensor circuit wiring, Poor ground connection, Low engine oil level or genuinely low oil pressure, Failed PCM/ECM (less common). The specific cause varies by vehicle.
How much does it cost to fix P0520 on a Subaru?
Published repair estimates on Subaru range from $200 to $3,500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0520 on a different make?
View P0520 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.