Speed, idle & inputs · Powertrain · generic (SAE-defined)
P0520: Engine Oil Pressure Sensor/Switch "A" Circuit
P0520 means the engine computer has detected an electrical problem in the engine oil pressure sensor or switch circuit, so it cannot trust the oil pressure reading.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0520 sets
The powertrain control module (PCM) monitors the signal from the oil pressure sensor or switch. If the circuit shows an open, a short, or a signal that is not possible for the sensor type, the PCM sets P0520. Because the code reflects the circuit, it does not by itself prove low oil pressure, but a genuine pressure problem must be ruled out. Monitoring details vary by manufacturer.
Common causes of P0520
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Failed oil pressure sensor or switch
- Damaged, oil-soaked, or corroded connector
- Open or shorted wiring in the sensor circuit
- Oil leaking from the sensor into the connector
- Actual low oil pressure from low oil level or wear
P0520 symptoms
- Check engine light on
- Oil pressure warning light or gauge reading zero, maximum, or erratic
- Engine may run normally if pressure is actually fine
- Ticking or knocking if oil pressure is genuinely low
How P0520 is diagnosed
- Check the engine oil level and condition immediately
- Install a mechanical oil pressure gauge to confirm real oil pressure at idle and higher engine speed
- Inspect the sensor and connector for leaks, damage, or corrosion
- Check reference voltage, ground, and signal at the sensor
- Check wiring for opens and shorts back to the PCM
- Replace the sensor if pressure is confirmed good and the circuit tests normal
Typical fixes for P0520
- Replace the oil pressure sensor or switch
- Repair the connector or wiring
- Top up or change oil if the level is low
- Repair the underlying engine problem if pressure is genuinely low
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Manufacturer notes
Commonly reported on GM V8 trucks and SUVs, where oil pressure sensor failures are well known. Definitions can vary by manufacturer; check factory service information.
Related codes & warning lights
P0520 FAQ
What does code P0520 mean?
P0520 means the engine computer has detected an electrical problem in the engine oil pressure sensor or switch circuit, so it cannot trust the oil pressure reading. The standard definition is "Engine Oil Pressure Sensor/Switch "A" Circuit."
Can I drive with a P0520 code?
Only after confirming the engine actually has oil pressure. Check the oil level right away; if it is low, or the oil pressure warning light is on, or you hear ticking or knocking, do not drive. If oil level is correct and the engine sounds normal, drive minimally until a mechanic verifies pressure with a mechanical gauge.
Does P0520 mean my engine has no oil pressure?
Not necessarily. It reports a problem with the sensor circuit. Still, verify oil level and actual pressure before driving, because real low pressure can destroy an engine quickly.
Why is the oil pressure sensor leaking oil?
Sensors can develop internal leaks, letting oil wick into the connector and wiring. This is a common reason for replacement.
Keep researching
More speed, idle & inputs codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.