What protective device is designed to shut down the engine if oil pressure becomes low?

The oil pressure switch is the correct answer because its primary function is to monitor the engine's oil pressure. If the oil pressure falls below a certain level, indicating a potential issue such as low oil levels or a failing oil pump, the oil pressure switch is designed to send a signal to shut down the engine. This precautionary measure helps prevent severe engine damage that could occur from insufficient lubrication.

While the oil filter helps remove contaminants from the oil, it does not monitor pressure levels. The safety valve is generally related to pressure relief in various systems but does not specifically shut down the engine based on oil pressure. A temperature sensor monitors engine temperature, which is important for engine health but not directly related to oil pressure management. Thus, the oil pressure switch is crucial as it directly protects the engine by ensuring it operates within safe pressure parameters.