E.1 to E.3
Option fault
Mitsubishi Electric · Mitsubishi A500 Inverter
What does E.1 to E.3 mean?
The inverter output is stopped if a contact fault occurs at the connector between the inverter and a communication option, or if the communication option itself develops a fault. The numbers '1' to '3' indicate the specific option slot numbers where the fault is detected.
Source: Mitsubishi A500 Inverter
Open Manual (Page 201)