Replacement Internal Oil Sensor
Generator Guru says:
Before replacing this item, please check the Oil Sensor CDI. If your engine is not starting, remove the yellow wire from the oil sensor to the CDI, and try to start it again. If it starts you need to replace the external Oil Sensor CDI (not the internal oil sensor). Do not run the engine without the CDI for any length of time, as it cannot shutdown the engine if there is a problem with the oil pressure, which could result in damage to the engine.
If you do need a new sensor, it may also be advisable to replace the Oil Sensor CDI too. When Oil Sensors malfunction it often damages the CDI at the same time.