P0520: Engine Oil Pressure Sensor/Switch A Circuit
What to do
Treat this as urgent until proven otherwise. If the oil pressure warning light is on, or the engine is making any tapping, knocking or rattling noise, stop immediately and do not restart — running an engine without oil pressure destroys it within minutes, and it is not repairable afterwards. If the light is off and the engine is quiet, it is more likely to be the sensor, but have oil pressure measured with a mechanical gauge before assuming so. Check the oil level while you are waiting; it costs nothing.
What this code means
A circuit fault on the engine oil pressure sensor or switch. This code says the module cannot read oil pressure — it does not say oil pressure is low. That distinction matters enormously, because the consequences of the two are separated by the cost of an engine.
The difficulty is that you cannot tell them apart from the code alone. A vehicle with a genuine oil pressure problem and a failed sensor present identically on a scan tool, and the instrument cluster warning may be driven by the same sensor that has failed. The only way to know is to measure oil pressure directly with a mechanical gauge, which is a short job on most engines and the correct first step whenever an oil pressure code appears.
On engines with variable-displacement oil pumps the sensor is also a control input rather than only a warning device, so a fault here can genuinely reduce delivered pressure as well as report it incorrectly.
Likely causes
Start here
- Faulty oil pressure sensor · moderate
- Corroded or loose connector · easy
- Damaged wiring harness near exhaust heat · moderate
Less common
- Genuinely low oil pressure · specialist
- Broken wire in control circuit · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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