Lights 2 and 4 flashing on the IDL40 actually only means that it has run out of salt.
Once you refill the chamber (Left hand side of the base)
it will take 2-3 wash cycles to stop the error flashing.
As a double check, if you have this error, just check the condition of your glass ware. You will notice it is quite cloudy. There you go, free fix.
Knucle23
September 2008