Here are your parts
Parts for Whirlpool GU2400XTPT3 Dishwasher - AppliancePartsPros.comSee the attachment for the tech sheet.
Sounds like a water heating problem.
The unit is waiting for the water to heat up and reach a set point temperature and for some reason it is not doing this.
First try removing power for a couple minutes to see if this will reset the unit.
If this does nothing.
Remove power from the unit and check the hi-limit thermostat. It should be 0 ohms.
If OK
This step might be easier if you check it at the control board as you would probably have to pull the dishwasher out from under the counter to check just the heating element.
Unplug the unit and remove the inner door cover so you can get to the control board.
Check from P6 to the W-V (white/violet) side of the door switch.
Should be around 20 ohms.
Note that this checks the heater and the hi-limit thermostat.
IF OK
With power still off check across the door switch.
Should be 0 ohms when activated.
Also check that the latch is OK to be sure that the switch does close when the door is closed.
If OK
Check the thermistor, it is what measures the temperature.
P2-2 to P7, see the wiring diagram for the spec.
If OK then odds are that the control board is the problem.
If you do not own a meter, I would suggest you purchase a one. You can get a decent digital multimeter for under $20.00. You do not need fancy though it is nice if the leads are a couple feet long.
If it saves ordering one unnecessary part it has paid for itself and you end up owning a useful tool.
Most places will not let you return electrical parts so if you order it, you own it.
A couple things to watch when measuring ohms and continuity
1. Always remove power from the machine otherwise you could blow your meter.
2. Always disconnect at least one side of any device you are checking. This eliminates the possibility of measuring an alternate/parallel circuit path.
3. When checking for closed contacts and continuity use the lowest scale (Usually 200 ohms). Then try higher scales. This scale is 0 to 200 ohms so if the device you are measuring is 300 ohms this scale would show an open circuit which it is not, you are just measuring outside the scale's dynamic range.
4. When you start always short the meter leads together. This will tell you that the meter is working and if there is any 0 offset.
There is a good STICKY at the start of this forum about it's use.