Error code E1 on Diplomat ADP 8252 ???? Not in Manual?

Please will someone advise the meaning of error code E1. In the manual of the Diplomat ADP 8252, it lists that this error code is not used. We have cleaned the filters and checked the salt levels. When the machine is loaded and a program selected, it sounds as if the machine is working, however after a few minutes the machene bleeps and displays error code E1. Any help would be greatly appreciated.
Kind Regards
Jane
j4ne_home@yahoo.co.uk