Whirlpool ADP6830

Hi! Whirlpool ADP6830 dishwasher is showing F4 fault code - no idea what this means - have cleaned the filters etc. reset the machine but F4 every time - on a pre-rinse wash it doesn't sound as if water is actually going into the machine although all the pipes are clear ???
Can anyone help please? machine is out of warranty!!
Thanks!

F4 is a draining failure. Check that it actually drains. If it does, try taking out the filters and sieve and clean the black grill in the sump. Be careful cleaning it, it's a membrane and if punctured it's useless.