P0520 Code: Subaru Impreza (2017-2023) - Causes, Symptoms & Fixes

No recalls found in NHTSA database

No NHTSA owner complaints were listed for Subaru Impreza (2017-2023) specifically related to P0520, and there are no recalls shown for this make/model/year in the data provided. This means the guide relies on general P0520 diagnostics for Subarus plus typical maintenance knowledge, rather than a documented set of official factory fixes for this exact model/year combination.

CODE MEANING AND SEVERITY

• Code: P0520 — Oil Pressure Sensor/Switch Circuit
• What it means: The engine oil pressure sensor (or its circuit) is reporting an abnormal signal. This can be an actual oil pressure issue (low pressure or abnormal pressure) or a sensor/circuit fault (wiring, connector, or sensor failure).
• Severity: Moderate to high. If the oil pressure is truly low, continuing to drive can cause engine damage (bearing wear, oil starvation). If the fault is only the sensor or wiring, symptoms may be deceptive (warning light on despite normal pressure). Treat as a potential risk and diagnose promptly.

COMMON CAUSES ON SUBARU IMPREZA

• Faulty oil pressure sensor/switch or its connector (most common for P0520)
• Damaged, corroded, or loose wiring harness to the sensor
• Low or degraded engine oil level
• Poor oil quality or incorrect viscosity (wrong weight for your engine, or past its service interval)
• Clogged oil pickup screen or restricted oil passages
• Failing or worn oil pump (less common but possible)
• Internal engine wear or debris causing restricted oil flow
• Upstream issues (e.g., recent filter change, improper installation, or aftermarket mods affecting oil pressure readings)
• Sensor calibration drift or failed PCM interpretation (less common)

Notes for Subaru Impreza owners:

• Subarus often place the oil pressure sensor near the oil filter housing; wiring harnesses in this area can rub or corrode with age.
• Short trips, infrequent oil changes, and exposure to high heat can accelerate oil sludge or varnish, contributing to suspect pressure readings.
• If you’ve recently changed oil type/viscosity or are using a not-approved grade, this can affect measured oil pressure.

SYMPTOMS

• Illumination of the oil pressure warning light or check engine light
• Fluctuating or steady oil pressure gauge readings (if equipped with a gauge) or a dash warning
• Engine knocking or ticking noises due to actual low oil pressure
• Dull engine performance, reduced power, or intermittent misfires (in some drives)
• Oil smell, oil leaks, or visibly low oil level
• After resetting the code, the light returns after a drive (persistent), or the code reappears with the same symptoms

DIAGNOSTIC STEPS

Note: Start with the simplest, safest checks and progress to more involved tests. If you suspect real oil pressure is low, stop driving and address the issue promptly.

Step 1: Read codes and data

• Use a capable OBD-II scanner to confirm P0520 and read any related codes (P0521-P0523 can accompany P0520 and help clarify sensor range, low/high input, etc.).
• Check freeze frame data for engine rpm, oil temperature, vehicle speed, and fault status at the time of the code.

Step 2: Verify oil level, condition, and service history

• Check engine oil level with the engine cold or at least 5–10 minutes after shutdown (per manual). Top up if low with the correct viscosity for your engine.
• Inspect oil condition: should be clean and amber; sludge or very dark oil can indicate neglect or contamination.
• Confirm oil change history and service intervals; ensure the oil grade matches factory specification (viscosity and quality).

Step 3: Inspect sensor and wiring

• Visually inspect the oil pressure sensor and its connector for signs of damage, corrosion, or loose connections.
• Check the wiring harness for fraying, compromised insulation, or grounded contacts.
• Disconnect and inspect the sensor connector for corrosion; clean or replace as needed.

Step 4: Basic sensor test

• If you’re comfortable, unplug the oil pressure sensor with the ignition off and observe if the engine light behavior changes (some vehicles trigger a different fault when unplugged). Reconnect securely.
• If you have the equipment, test the sensor resistance and compare it to the manual’s specified range across temperature; note that many P0520 tests rely on the PCM interpretation rather than a fixed resistance.

Step 5: Mechanical oil pressure check (recommended if you suspect actual low pressure)

• Perform a mechanical oil pressure test using a calibrated mechanical oil pressure gauge:
  • Locate the oil pressure test port or adapter fitting (manufacturer service manual can show exact location for the engine in your Impreza).
  • Install the mechanical gauge in place of or parallel to the sensor, ensure a proper seal, and run the engine to normal operating temperature.
  • Take readings at idle and at specified RPMs (e.g., 2,000–3,000 rpm) and compare to Subaru service specs for your engine variant (notes: specs vary between 2.0L and 2.5L engines and across model years; refer to the official service manual for exact numbers).
• If measured oil pressure is significantly below spec:
  • Investigate mechanical causes (oil pump, pressure relief valve, screen/clog, worn bearings).
• If measured oil pressure is within spec but the sensor still reports a fault:
  • Sensor replacement or wiring repair is likely.

Step 6: Inspect oil pump and related plumbing (if pressure is low)

• Check for blockages in the oil pickup tube, screen, or oil passages.
• Inspect the oil pump for wear or failure if practical (this is typically a more involved repair).

Step 7: Rule out external causes

• Ensure there are no external oil leaks that could affect oil pressure sensor readings or oil level.
• Confirm there’s no engine oil consumption issue causing low oil level.

Step 8: Clear codes and retest

• After any repair or sensor replacement, clear codes and drive normally to confirm the issue is resolved and no new codes appear.

RELATED CODES

• P0521: Oil Pressure Sensor Range/Performance
• P0522: Oil Pressure Sensor Circuit Low Input
• P0523: Oil Pressure Sensor Circuit High Input
• Other engine codes (e.g., P0300 misfires, P0171 fuel mixture) may appear if the PCM reacts to pressure irregularities or poor engine performance related to oil pressure.

REPAIR OPTIONS AND COSTS (2025 PRICES)

Note: Prices are estimates used by independent shops and dealers. Actual prices vary by region, labor rate, engine variant (2.0L vs 2.5L), and whether components are replaced as a package.

A. Oil pressure sensor replacement (most common)

• Parts: $20–$60
• Labor: 0.5–1 hour
• Total typical range: $100–$250 (independent shop)
• Dealer: $150–$350

B. Sensor wiring/connector repair or harness replacement

• Parts: $0–$60 (depends on if only wiring is replaced)
• Labor: 0.5–1.5 hours
• Total: $100–$250

C. Oil change and fluid refresh (baseline maintenance)

• Parts: Oil and filter: $25–$70 depending on synthetic or conventional
• Labor: $0–$40
• Total: $40–$110

D. Mechanical oil pressure test and sensor confirmation

• If you’re performing this yourself, cost is limited to tool use; otherwise, negligible as a separate line item beyond standard diagnostic time.

E. Oil pump replacement (less common; significant repair)

• Parts: $120–$350 (pump plus seals)
• Labor: 3–6 hours (Varies by engine, access)
• Total: $600–$1,500
• Note: In cases of actual pump failure, this is the primary fix.

F. Oil pump or pick-up screen cleaning/repair (if oil flow is obstructed)

• Parts: minimal
• Labor: 1–3 hours
• Total: $150–$500

G. Engine overhaul or rebuild (rare; driven by actual oil starvation damage)

• Cost: Highly variable and expensive; thousands to tens of thousands
• Typical outcome: Not a first-line repair for P0520; should be considered only if mechanical damage is confirmed.

Tips:

• If the car is under dealer warranty or certified pre-owned, check coverage for components related to oil pressure (sensor, wiring, or pump).
• Always reconnect components properly and torque fasteners to spec when replacing sensors.

DIY vs PROFESSIONAL

• DIY-friendly tasks (if you are comfortable and have basic tools):
  • Check oil level, top up, and change oil and filter if due.
  • Inspect sensor and connector visually; replace sensor if you’re confident in locating and replacing it.
  • Accessing and verifying sensor wiring connections.
  • Basic or medium-level diagnostic checks with a good OBD-II reader.
  • Conduct a basic oil pressure test if you have mechanical gauge and adapters appropriate for your engine.
• Professional tasks (recommended if you suspect genuine low oil pressure or internal engine issues):
  • Mechanical oil pressure testing with accurate gauge and procedure.
  • Replacing the oil pump, pickup screen, or performing engine internal checks.
  • Thorough wiring harness diagnosis and possible PCM reflash if sensor data is being misinterpreted.
  • In cases where there is actual engine wear or sludge, a professional teardown and inspection plan is necessary.

Safety note: If you observe a bright warning light for oil pressure, or if you hear unusual engine noises, pull over safely and assess oil level and condition before continuing. Low oil pressure can cause severe engine damage quickly.

PREVENTION

• Follow Subaru’s recommended oil change intervals and use the approved oil grade for your engine variant (check owner’s manual or service manual).
• Use high-quality oil and new filters; avoid “off-brand” or incorrect viscosity beyond spec.
• Regularly inspect oil level and look for leaks; address any leaks promptly.
• Avoid frequent short trips that don’t allow oil to reach full operating temperature—this can encourage sludge and pressure sensor issues over time.
• Periodically inspect the oil pressure sensor and its wiring for signs of wear, corrosion, or damage, especially on higher-mileage Subarus.
• Schedule proactive maintenance: oil changes, filter changes, and fuel/air conditioning system checks to ensure overall engine health.

DATA LIMITATIONS

• The provided data shows no official NHTSA recalls or complaints for the 2017-2023 Subaru Impreza related to P0520. This guide uses general P0520 diagnostic principles and common Subaru implications rather than a documented, model-year-specific official remediation plan. Real-world results can vary; if you notice persistent symptoms or genuine low oil pressure, treat it as a critical issue and seek professional evaluation.