If your inverter shows grid code faults, check that the correct UK setting (G98 or G99) is selected, not a different country's standard. These codes range from temporary issues that clear themselves, such as brief grid fluctuations, to serious faults requiring professional attention. Understanding what common error codes. The Alarm Code Maintenance dataset provides a comprehensive reference of alarm, fault, and warning messages used across grid-connected inverters, energy storage systems (ESS), batteries. Use a multi-meter to check the voltages between PV+ and earth, PV- and earth of all the PV strings. Added 4000 Inverter Communication Error. About 80% of the errors I've dealt with on my own systems and helped others troubleshoot came down to a loose connection, an overloaded circuit.