Epson Apex 20020 - Manual (Page 162)

Display Card Check
The computer checks the color or monochrome display card
that is installed in the system. An error number and message
appear if any faults are found in the display adapter card.
Number 401 represents an error in the monochrome display
card, and 501 represents an error in the color display card. The
messages are:
401-CRT
error
501-CRT error
Optional RAM Check
If any additional memory (expansion RAM) is installed, the
computer then checks that RAM for any malfunction.
Diskette Drive Seek Check
The computer checks its diskette drives by searching the
read/write heads for any malfunction.
If any seek errors are found, you see this message:
601-Diskette error
If this message appears, run the System diagnostics (described
in Appendix C) and select the Floppy disk drives and
controller test, option 6, from the DEVICE LIST. If the error
persists, consult your Customer Care Center about having the
drive repaired.