Mitsubishi Electric FR-A7NC Instruction Manual page 43

INVERTER SETTING
(2) Measures at error occurrences
Fault Indication Error Definition
Communication line
E.OP1, E.OP3
error
E.1, E.2, E.3 Option fault
When faults other than the above are displayed, refer to the inverter manual and remove the cause of the error.
36
Check the LED status of the option unit and remove the cause of the
alarm. (Refer to page 96 for LED indication status)
Inspect the master.
Check the connection between the inverter and option unit for poor
contact, etc. and remove the cause of the error.
For the FR-A700 series, fit the communication option in the option
connector 3.
Measures