Whirlpool adp2315sl

whirlpool dishwasher adp 2315 drain pump activates in short duration,about eight times then fault code of eight flashes displays, have checked filters and drain hose.machine does empty, could this be a reed switch problem as there is no water entering the machine. Or am i barking up the wrong tree. This is not a built in machine,but they have built round it, so looks a nightmare to get out, hence looking for a point in the right direction.
Thanks
Darren