An oil-pressure sensor, or switch, is usually incorporated onto a car's engine block near its oil filter. The sensor is used to trigger a warning light on a car's instrument cluster when oil pressure is too low.
Also called an oil-level sensor, the oil-pressure switch can sometimes malfunction by misreading a car's oil level. When this error occurs, a "low oil" light might come on, or the switch might fail to turn the light on when a car's engine-oil level is too low. This malfunction is a problem because oil lubrication is crucial for all vehicles.
Repair Pal notes that some vehicles have an oil-pressure gauge either instead of, or in addition to, an oil light.