I have followed instructions in manual and still have the code above. water pressure and flow rate good.
Filters cleaned.
Could you please advise which part may be making this fault ?

John Harris, November 2008

Hi I had the same problem after reading the advice here I checked my machine, I didn't have a pressure switch but I did notice a small wire going into the valve was broke, so I just fixed that wire and boom error gone.

Jay, Dublin, July 2014

I had the same. It also overflowed if left running.
The water pressure was fine and the wash cycle went through, but flashed H20 throughout.
I took the lid off - two screws at the top back, then slide from front to back (might need a thump to move at first).
When looking at it from the front, halfway down the right there is a red pressure switch. This measures water in and out by measuring air pressure in and out.
Tap this with a screwdriver and H20 disappears and the machine bursts into life.
I replaced this with a part from http://www.hotpoint-spares.co.uk which cost ~£12 INC VAT and Delivery and it's been fine ever since.

john in Hull, November 2011

The error code is as you say for water entering the machine or not as the case may be. Although you have plenty of water pressure is any of it getting into the machine? you could have a valve fault!

casper...http://selfix-uk.co.uk, November 2008