Just had the same problem on mine. E3 basically says "you didn't do the procedure correctly". Well, duhhhhhhh!! That's no help.
E7 is "Mode Error", meaning some set of instructions was incomplete, probably in the programming (P) mode.
To clear it: turn key to P mode. Hit NS key.
Now reprogram the instructions, if that's what you were trying before this happened, or go to the R mode and try performing normal sales, etc.
If that doesn't work, turn key to P mode, hit NS. Then turn key to Z mode, hit NS. Do this for every position of the key switch.
If that doesn't do it, you will have to do a "Master Reset", then completely re-program the register.
automan53, September 2009
