Thanks akubra_lands, it worked for me too on model DW28W. I thought I should elaborate on your answer for anyone else who comes across this while researching the same problem.
The repair is ridiculously simple (takes about 10min) and the only tools needed are 1 philips/posidrive screwdriver and 1 flat blade screwdriver. Assuming you've unplugged it from mains power:
- Tip the dishwasher on its right hand side (looking from the front).
- Remove 4 screws from the metal base - 2 front and 2 rear (the rear ones have anti-rattle washers on them).
- Pull the base away, taking care of the pair of wires leading to the flood indicator float switch which is still attached to the base.
- Remove all 4 screws which fasten the solenoid valve to the pipe which leads from the pump upwards to the center of the tank (which feeds the lower spray arm).
- Pull the solenoid/valve body off the pipe and you will see it has a whitish plastic flap with a hinge at the top end.
- Use the flat blade screwdriver to gently prize open one side of the flap hinge and twist the flap until it is completely free of the valve body. Put the flap to one side.
- Replace the valve body, without the flap, and secure all 4 screws.
- Reassemble the dishwasher. Done
Now take a moment to admire the handiwork of the engineer who planned the failure of that innocent little plastic flap around 6 months after the expiry of the warranty.
I actually had a repair man come and look at the problem, and yep, right on cue, he told me it needed a new pump motor. $300. When he realised I was on to him he just gave up. So hard for repair people to do an honest day's work these days..