We put the valve under the dash so to speak, where it is easy to get to. It is the return line that also powers the jet pump. I am not sure what the full fix would be. This solved our problem and it is an old forklift that I already had put to much money into. As for the sensor I have no idea, not even sure if it has one. You can access part schematic's on line that should help you find it if there is one. Good luck!