This answer 8 years too late to help you original chaps in this posting ...but I hope this may help others.
I recently had the same issue with my 15yr old WD71, Error Code E15 "Check Outlet Pipes", and machine not progressing into the intermediary spin cycles after initial wash. After checking "everything" ( outlets, level diaphragm sensor etc ) I was just about to give up, then happened on a single posting on the web , which I since cant relocate (!) by a former Hotpoint Engineer who mentioned that a damaged or corroded heating element could be responsible... apparantly any small damage or pinhole corrosion in the outer skin of the element can cause the inside of the element to become slightly wetted . . just enough enough for an electrical leakage to earth .. in turn this being responsible for a false signal interpreted by the control board. The easy check , for me, was to pull of the front, disconnect both sides of the element connections ( insulation-taping them over well, of course ) then running the machine through a wash cycle with the elemnt disconnected. This Cured the problem ! So a new aftermarket pattern element was purchased off flea-bay, fitted, and the issue is now resolved for the last 3 months.
Coincidentally, this also seems to have fixed a seperate issue :- what I had thought was a dodgy door catch solenoid ... which previously had been "chattering away", but required machine to be switched off before it would finally come to rest "unlocked". That issue vanished at the same time.
Hope this helps someone out there :-)
Nic P
May 2017