Miele W562 sump pump runs continuiously,soak/prewash flashes

[cmcm3]

Miele W562 washing machine purchased in 2009. (4.5 years old?). Used on average one wash per day.
Out of warranty.

When turned on the sump pump comes on and runs continuously. After a minute or so the soak/pre-wash light starts flashing, motor keeps running continuously.

The machine does actually drain water completely.

I've checked the following:
Sump pump drains water completely
Float ball in sump moves freely and creates a seal when water is all drained.
No blockage in "pressure chamber" or hose to pressure switch
Pressure switch hose seems in good condition

Based on this I fear that the fault lies either with the pressure switch (mounted on the main PCB) or the PCB itself. This is around the €400 mark according to miele parts department. (in addtition to callout fee)

Before I decided whether to dump machine or call out Miele, can anyone tell me:
Is there anything I'm missing that could cause this?
Is the machine looking for atmospheric pressure at the switch to indicate draining finished? If that's the case, can I confirm the diagnosis by disconnecting one end of the pressure switch hose?

 

[RichardMNZ]

It does sound like a sensor issue.


This sounds gross but can you disconnect the tube that connects to the pcb and blow? Is it clear? What is the effect if you disconnect the other end of the hose and suck? (I told you it sounds gross..)

You may want to check the hoses that go from the pump to the water inlet chamber are clear too. There is a Y connector that can get gummed up too

 

[RichardMNZ]

It does sound like a sensor issue.


This sounds gross but can you disconnect the tube that connects to the pcb and blow? Is it clear? What is the effect if you disconnect the other end of the hose and suck? (I told you it sounds gross..)

You may want to check the hoses that go from the pump to the water inlet chamber are clear too. There is a Y connector that can get gummed up too

 

[cmcm3]

It does sound like a sensor issue.


This sounds gross but can you disconnect the tube that connects to the pcb and blow? Is it clear? What is the effect if you disconnect the other end of the hose and suck? (I told you it sounds gross..)

You may want to check the hoses that go from the pump to the water inlet chamber are clear too. There is a Y connector that can get gummed up too

Well, I didn't notice any blockages or air leaks on the pressure hose. The other tubes and y were all fairly clean as well.
However I turned off the machine after checking this and when I turned it on this morning , maybe 10 hours later, the drain pump didn't run and I've been able to run it through 2 full washes since.
I'm guessing the control module was stuck somewhere in program and that I somehow reset it. It must have been something more than just turning off overnight to reset it as i'd left it off longer than that over the weekend without any effect.

thanks for the help.