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Parts for GE EDW6060L00SS Dishwasher - AppliancePartsPros.com

Disconnect the wires from the water inlet valve and attach your meter leads to them. Make sure that they cannot short to each other or the frame.

Now try a cycle, if you see 120 volts across the valve wires when it should be filling then odds are that you have a bad connection or contact set somewhere in the wiring.

Here is my thoughts on this if I read your post correctly. You see 30 volts across the valve when it should be filling so it is dropping 90 volts somewhere else in the wiring due to the current pull. This could be pitted contacts or a bad (loose or dirty) connection.When you attach just the meter there is very little current flow so you see the full voltage.

Remove power from the unit set your meter on it's most sensitive meter scale. Short the meter leads together before you start masuring so you know what if any zero offset the meter has.

Remove both wires from the overflow switch and measure the switch contacts. They should be 0 ohms when the switch is activated.

If OK
Remove the wires that go to the valve/overflow switch at the control board.
Short the wires for the valve and the switch together then check the resistance, should be 0 ohms.

It may also be the valve itself but I would have thought it would blow a fuse if the valve was dropping the 120 down to 30 volts but who knows they may have a current limiting device on the board.