Mitsubishi Electric LS Pro Hardware Technical Reference page 133

In addition to the error beep codes above the video BIOS on the revision D system
board can return the following two error codes:
1-2
1-3
Error messages which appear on the screen are in text form, not error codes. The
appropriate action can then be taken. For example:
Error message
Not a boot diskette - strike F1 to retry boot
Action
Insert correct disk and reboot
Error beep codes
Old video adapter failed
Checksum failure/DAC failure/RAM error
LS PRO HARDWARE TECHNICAL REFERENCE C/3