I had the same Error in my Machine, try to start with 2&8 with USB-Stick, then Format HDD and Flash, Transfer the Firmware with Update (Backless Mode).
After this the Firmware was installed on the System, after Reboot E602-0001 appears, made a HD-Clear (when E602-0001 appears take the *28* as describe in the Servicemanual, you have an Option to Clear the HDD)
Now the System ist working fine, the Printer starts up and everything is ok.