Display Message E2?

I have a Diplomat ADP 8224 - probably 8 yrs old now. If I put any program on I hear 2 beeps which is normal, then 5mins of swooshing water but then 4 bleeps, then 1min of water sounds again and then the machine stops. Goes no further. E2 message displayed, but my manual only lists, E1,E3,E4,E5, E6. Have cleaned thoroughly, checked all filters and inlets, filled with salt and rinse aid, No joy! Any ideas?