Mitsubishi Electric Melsec-Q172DCPU User Manual page 210

6 INSPECTION AND MAINTENANCE
1)
Did the
7-segment LED display
"AL" "L01"?
YES
Write the project data to the Motion
CPU module.
Reset the Multiple CPU system
Does
"AL" "L01" disappear
on 7-segment LED
YES
END
6 - 21
NO
A hardware fault
Check operation in the order starting
with the minimum system.
If the module will not work, explain
the error symptom and get advice
from our sales representative for the
modules with failure.
(f)
NO
Flowchart for when "AL"
displays on 7-segment LED
"L01"