If it's already been mentioned, sorry but I've also read where you can take a bag or two of ice, put it in the toilet and while underway, let the ice clean the tank sidewalls and sensors. I've never done it but I can see how it might work.
Mike, Sue, Sissy and Little Man
2015 Ford F350 Lariat FX4 6.7 CC DRW
2015 Eagle Premier 351RSTS