Mitsubishi Electric MELSEC-Q Series User Manual page 213

POINT
If data link cannot be performed even though no error is indicated in the "System
Monitor" window, select the Simple Motion module, and click the [Diagnostics]
button. (Refer to (b).)
(a) Checking for error in modules other than the Simple Motion module
1) Select a module other than the Simple Motion module in the "System Monitor"
window, and click the [Diagnostics] button.
The window corresponding to the module will open. (The CPU module is
selected in the illustration below.)
If the [Diagnostics] button is not supported by the module, click the [Detailed
Information] button.
When data link cannot be performed even though no failure is shown in
"System Monitor", select the Simple Motion module and click the [Diagnostics]
button.
12 - 3
Chapter 12 TROUBLESHOOTING