Search button will be your friend.....topic has been discussed to great extent. Enough reading in previous threads to last you a long time...short and sweet.....sensors are far from reliable and many people simply learn how to operate with them being inaccurate. You can attempt several cleaning techniques described in posts, some work some don't and at the end of the day the sensors may still be inaccurate simply due to "stuff" like greases an oils that get stuck to the sides of the holding tanks.
2016 Chevy Silverado 2500 Duramax
2016 Rockwood 8289WS, Diamond Pkg.