Have water to the dishwasher valve. I checked dishwasher float and appears free and switch is working. Pput volt meter on dishwasher valve and have 110 volts when unit is turned on, but voltage drops to 40 volts during fist cycle.
Go to your main power wire connection feeding dish washer, remove wire nuts, and put your meter there, when it’s off, which you should get 120v.
Turn on, and see if it drops there. Post back your findings.
Here are your parts
http://www.appliancepartspros.com/partsearch/modelsearch.aspx?model=DU915PWPQ2
Here is the tech sheet
http://www.servicematters.com/docs/wiring/Tech%20Sheet%20-%208535431.pdf
The valve should have opened when it had 110 volts across it so I would say it needs replacing.
Only other possibility I can think of is a plugged screen filter on the input side of the valve. Remove the valve from the unit and check/clean the screen.
If OK replace the valve.
If dirty do not remove it permanently from the unit as it is there to keep crud out of the vavle which would hold it open and cause a flood.
Cannot explain the 40 volts, it could have been ghopst voltage but seems a little high.