whirlpool adp4502/5 4 flashes

Hi our whirlpool adp4502/5 dishwasher has 4 flashes from reading the threads I think its drain not detected in the time allowed, I’ve cleaned everything but I can’t get at the black bit at 3 o’clock, the threads say its a twist fit from underneath, but I can’t get at it to remove it. How do you get at it from underneath? Is this access through the sump or from through base of mmachine? I’ve used a t20 to remove screws from bottom arm to see if that would help gain access but didn’t work. I’ve tried bicarb, white vinegar and boiling water. I’ve also tried squirting hot water at the black bit at three oclock. I’m starting to think I’ve been defeated! Please help it can’t be that hard to fix can it?