P0520
Engine Oil Pressure Sensor/Switch Circuit MalfunctionP0520 is a generic OBD-II powertrain diagnostic trouble code: Engine Oil Pressure Sensor/Switch Circuit Malfunction. It is logged by the engine control unit when the throttle monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0520 means
P0520 is a generic SAE OBD-II fault code that indicates a problem with the Engine Oil Pressure Sensor/Switch Circuit. It is set when the Powertrain Control Module (PCM) detects that the voltage signal from the oil pressure sensor or switch falls outside the manufacturer's expected range, or when the signal is absent or erratic. The sensor's role is to convert actual engine oil pressure into a voltage reading the PCM can interpret to confirm that internal engine components are receiving adequate lubrication.
It is critical to distinguish between a faulty circuit/sensor and genuinely low oil pressure, as both conditions can trigger P0520. A defective oil pressure switch or damaged wiring can produce a false low-pressure signal even when actual oil pressure is normal. Conversely, a correct sensor accurately reporting low pressure indicates a real mechanical problem — such as a failing oil pump, worn engine bearings, or severely degraded oil — that poses an immediate risk of engine damage.
Because P0520 can represent either an electrical fault or a serious lubrication failure, it must never be dismissed without verifying actual oil pressure using a mechanical gauge. The PCM may respond to this code by commanding a forced engine shutdown (paired code P2105) to protect the engine, which can prevent the vehicle from restarting until the fault is resolved.
Common causes
Most-frequently reported root causes when P0520 is logged.
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1
Faulty or worn oil pressure sensor or switch
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2
Corroded, damaged, or disconnected wiring/connector at the oil pressure sensor
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3
Actual low engine oil pressure (low oil level, degraded oil)
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4
Wrong engine oil viscosity or grade
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5
Failed or weak oil pump
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6
Worn engine bearings causing insufficient oil pressure
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7
Failed oil pressure relief valve
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8
PCM software fault or, rarely, PCM failure
Symptoms drivers notice
How to diagnose P0520
A typical diagnostic flow when this code is present.
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1
Read and record all stored fault codes and freeze frame data; note engine oil level and condition before starting
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2
Check the engine oil level and quality — if low or severely degraded, correct this first and recheck before proceeding
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3
Inspect the oil pressure sensor/switch connector and wiring harness for corrosion, chafing, or disconnection; repair any faults found and re-scan
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4
Measure sensor circuit voltage and resistance against manufacturer specifications using a multimeter
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5
Install a mechanical oil pressure gauge at the sensor port and verify actual oil pressure at idle and at 3,000 RPM against factory specifications
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6
If actual oil pressure is within spec but the code persists, replace the oil pressure sensor/switch and retest
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7
If actual oil pressure is low even with good oil level and fresh oil, inspect the oil pump, pressure relief valve, and internal engine components for wear
Related powertrain codes
- P0120 — Throttle Position Sensor/Switch A Circuit Malfunction
- P0121 — Throttle Position Sensor/Switch A Circuit Range/Performance Problem
- P0122 — Throttle Position Sensor/Switch A Circuit Low Input
- P0123 — Throttle Position Sensor/Switch A Circuit High Input
- P0124 — Throttle Position Sensor/Switch A Circuit Intermittent
- P0220 — Throttle/Pedal Position Sensor/Switch B Circuit Malfunction
Frequently asked questions
Can I keep driving with a P0520 code?
Not safely. Because P0520 may indicate genuinely low oil pressure, continued driving risks severe engine damage from inadequate lubrication. Check the oil level immediately and have the fault diagnosed before driving further. If the oil pressure warning light is also on and/or the engine is making knocking noises, stop the engine immediately.
Is P0520 always caused by a bad oil pressure sensor?
No. While a faulty sensor or wiring is the most common cause, the code can also be triggered by actual low oil pressure due to low oil level, degraded oil, a failing oil pump, or worn engine bearings. Confirming actual oil pressure with a mechanical gauge is an essential diagnostic step before replacing the sensor.
How do I tell if the sensor is bad or if my engine has low oil pressure?
The only reliable way is to connect a mechanical oil pressure gauge directly to the engine in place of the sensor. If mechanical pressure is within the manufacturer's specification but the PCM still reports a fault, the sensor or its circuit is the problem. If mechanical pressure is low, the fault lies with the lubrication system itself.
Will the engine shut itself off because of P0520?
It can. Many modern PCMs are programmed to command a forced engine shutdown (often logged as companion code P2105) when they detect a sustained oil pressure fault, to prevent catastrophic engine damage. This may leave the vehicle unable to restart until the underlying fault is repaired.
Disabling P0520 in software
RaceTune can permanently disable P0520 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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