The F20 error means the main control has killed the cycle because there was no water detected entering the machine. The pressure switch is what determines when the machine has enough water in it, if the pressure switch was not tripped within a 6 minute time frame the control kills the cycle. It does this as a safety precaution in case the pressure switch is bad and it's not shutting water supply off to the washer which would could flood your home. Unplug the washer and follow the troubleshooting steps below.
Verify your water is on and that there is water pressure being supplied to the washer. Remove the water supply lines from the washer and check that the screens on the water inlet valve and water supply lines are not stopped up and are clean. If they looked corroded or stopped up clean them and this will probably fix the problem.
Make sure the washer is not constantly draining water while its filling due to a vapor lock on the drain on your home. Make sure there is small gap between the drain hose and the drain to ensure the drain can breathe.
Check the connections and wiring between the water inlet valve, pressure switch, flow meter and the central control unit.
Blow air through the flow meter while checking resistance, make sure its a closed circuit when doing so.
The parts you may need to fix this F20 error are the water inlet valve, flow meter and the water level pressure switch. These Whirlpool Duet Washer parts can be ordered from the link below. The links also provide instructions to change the parts.
Click Here To See The Water Level Pressure Switch Part Information
Click Here To See The Flow Meter Part Information
Click Here To See The Water Inlet Valve Part Information
This Whirlpool Duet Washer F20 error troubleshooting and repair information applies to model WFW9200SQ00 and all the models listed under the related models section below.