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Replacement parts for MAYTAG MDB7130AWB DISHWASHER- UNDERCOUNTER | AppliancePartsPros.com

I cannot really help with the turbidity sensor.
But that the top arm does not rotate seems to indicate that the problem is elsewhere.

Check the parts breakdown to ensue you have cleaned all filters/

A common problem is the unit not filling with enough water.
Most units fill to just under the heating element.
This can be checked by adding a couple quarts of hot water after each fill during a cycle. If it now washes OK then check the fill valve.
Just be careful to not overfill it.
Often if the fill is low you will also hear a growling sound because the pump will cavitate (suck in air).
The most common cause is a dirty screen filter on the input side of the fill calve. Remove the valve from the unit and clean/check the filter.
Do not permanently remove it from the valve as it is there to keep crud out of the valve which could hold it open and cause a flood.

If it still does not fill correctly I would replace the fill valve.

PS: Be sure to shut off the power and the water supply to the unit. Have paper towels etc. handy to wipe up any spilled water. Get a small pan/bowl etc. that will fit under the valve then loosen the input water line let it drip into the container emptying it as necessary. This will minimize the amount of water spilled.