I have a 2005 31ss granite ridge. I just bought it the fall and none of the tanks will read anything but empty no matter if they are half full or all the way full. The grey water tank is the only one I'm not sure how to check but fresh water i fill till it comes out of the overflow tubes above the driver side rear tires and black water tank I just look in the toilet to make sure it is full.They always show empty.Just wandering if anyone has had this problem before? Is there an easy fix?What is the best way to access the tanks so I can replace or work on the sensors? Any information would be greatly appreciated. Thanks Brian.