My washing machine won't drain and says F4 on display?

Hello
My washing machine won't drain and says F4 on display, I have checked the filter at the front and it is clear.
The serviceman opened the washing machine, checked motor and the two of it 's board. He said all of them are ok. but when i turned on the machine, after 2 or 3 minutes, it stopped cycling and said f4 on display.
when i turned it on, i knew something was strange. it cycled slowly and stopped for several seconds then cycled and again it stopped for several seconds, these actions repeated 4 or 5 times, after that machine stopped and show F4.
would you please help me, I am from iran and don not know what should i do. my serviceman con not help me anymore.
thanks alot