Epson LT-286 - Manual (Page 124)

If there are faulty RAM chips in your system, you see one of these
messages:
201-Memory error
202-Memory address error
203-Memory address error
If an I/O or parity error occurs, you see one of these messages:
Parity check 1
Parity check 2
The program also displays the number of the segment causing the
problem.
Keyboard Controller and Keyboard Check
The computer checks the keyboard controller and keyboard for
problems such as failure of one of the keys to release. If there are
any errors in the connection between the keyboard and computer,
you see this message:
301-Keyboard error
When this message is preceded by a number (
XX
), the number
represents the key (in hexadecimal) that is the source of the error.
If another failure is found, you see one of these messages:
303-Keyboard or system unit error
304-Keyboard or system unit error
Video and Video Controller Check
The computer next checks the video and video controller. If an
error occurs, you see this message:
401-CRT error
501-CRT error
Power-On Diagnostics C-3