Whirlpool DWF 407 IKEA Dishwasher ser...

Hello.
I hope someone can help us with this weird behavior of our dishwasher: It is a Whirlpool DWF 407 that we bought at IKEA 4 years ago. It worked fine for 3 years without having used it more than 3 times a week.

The machine first started about a year ago to not finish cycles (after 80% - beeping twice and blinking LED - usually before pumping water)
I managed to bridge the problem by running the ''END'' program that pumps off the water. This became frequent after a while.

Next the machine did not start cycles at all (on all programs the same): It pumped for 20 seconds, then again beeping twice and blinking. I managed to bridge this problem by pouring 5-10 liters of water into the machine before starting the program (so the pump would have something to pump) This worked only on the ''rapid'' program, but at least it would start cleaning. Then the program would run its usual 80%. I still would have to ''manually'' finish the cycle by running the END program.

Now it does the same on all programs - even the ''END'' program - with or without additional water poured inside before: It pumps for 20 seconds, then beeping twice and the LED blinking - that's it.

What can we do? Is it a mechanical or electronical problem? Getting a technician and replacing parts does not seem an option as the price for that will get close to buying a new machine. I apretiate any kind of suggestions. Than you very much!
Max