The tank level sensors are simply screws thru the side of the tank at different levels. They are connected to sensitive electronics that sense a low resistance connection between the level sensor and ground. If paper or other crud stick to a sensor and touch the ground it will register as full to the level of the gunked up sensor. There are many ways to clean the sensors , but there is no sure way. Try adding 1-2 gallons of hot water and 1/2 cup of dishwasher liquid before your next trip. When you get to your destination empty the tank.
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