Topic that keeps showing up, and I'll bet that most of the responses will be
IGNORE the sensors, they rarely work.
We do use some Calgon water softener stuff (a laundry detergent additive, not bath beads) and a bit of laundry soap in our tanks when we run down the road, with say, ohhhh, 2 to 4 gallons of water for the slosh effect. It helps some, but, we don't do so for the sensors, but, for general cleaning.
Some have added some nice exterior type sensors, they are a bit pricy, but, reports are that they work.
For us, Calgon and All and away we go~! Snicker, maybe we are having a Calgon minute, "Take me away Calgon."