Epson 10020 - Manual (Page 157)

Floppy Disk Drive Seek Check
Finally, the computer checks its diskette drive(s) by searching
the read/write heads for any malfunction. If it finds any seek
errors, you see this message:
601-Diskette error
If this error occurs, make sure you have inserted the system
diskette into drive A. If this message still appears after you
insert the diskette, run the System diagnostics (described in
Appendix D) and select option 6 from the DEVICE LIST. If
the error persists, consult your Customer Care Center about
having the drive repaired.
C-4 Power-on Diagnostics