Error code 4 on Hoover AI130?

Hi, Can anyone help please? On my Hoover AI130 / AL130 Hoover Six 1300 Sportswear I got an Error Code 4. The machine was full of water and stopped. I drained down the machine and cleaned out the filter. Some debris in the filter but not much. Then removed top of machine and tested air valve by blowing down it - it clicks so I assume it is fine. All wires appear to be connected. What else can it be or what can I check? PCB?
Many thanks.