Code F I Have A Indesit Evolution 1300 WE13 Washing Machine That Keeps Flashing Up With The Error Code F-01. HELP!?

I have a Indesit Evolution 1300 WE13 washing machine that keeps flashing up with the error code F-01. HELP!? - code f

I had to change the water on him, but that was okay. Just flash with F-01 and refuses to do anything. What on earth does this mean and how I can solve this problem?
Any help would be greatly appreciated, very much!