In a diesel generator, the system shuts off the fuel supply if the oil level is too low with the help of an oil level sensor. The oil level sensor continuously monitors the oil level and oil pressure in the engine. If the oil level falls below a certain limit, the sensor sends a signal to the electronic control module (ECM), which in turn cuts off the fuel supply to the engine. This is done to prevent the engine from running with insufficient lubrication, which can cause damage and lead to costly repairs. Additionally, some generator models also have an automatic shutdown system that shuts off the engine if the coolant level is too low or if the engine is overheating.