| 3 01 | EEPROM (memory) error of the PCB. | The EEPROM memory of the main PCB is damaged or corrupted; if after a reset the 3 01 reappears without external faults, the PCB is responsible. Check for stable voltages on the PCB and, if necessary, reprogram or replace the PCB. |
| 3 02 | Communication error (GP–GIU). | Loss of communication between the main PCB (GP) and the interface/display (GIU), often due to a fault in the PCB itself. Check BUS wiring and power supply; if the issue persists, the technical documentation suggests replacing the PCB. |
| 3 03 | Main PCB fault. | Internal fault of the PCB (hardware/firmware) preventing equipment control; the self-diagnosis indicates "Main P.C.B. error". Confirm by ruling out external shorts and measuring 230 V/5 V on the board; if it persists, replace the PCB. |
| 3 05 | PCB fault. | Internal fault of the main PCB; the unit labels it as a PCB fault. Check power supply and connectors; if it persists after reset, replace the PCB. |
| 3 06 | Main PCB fault. | Internal fault of the main electronic control. Check voltages and absence of peripheral short circuits; if the error reappears, replace the PCB. |
| 3 07 | Main PCB fault. | Internal fault of the PCB detected by self-diagnosis. Confirm power supply and wiring; if it persists, the solution is to replace the PCB. |
| 3 09 | Gas relay check fault. | The gas valve relay is on the PCB; the self-check detects stuck contacts or control circuit out of tolerance. Verify activation and continuity of the relay on the board; if there is degradation of SMD components or the fault persists, replace the PCB. |
| 3 23 | PCB system fault. | Systemic fault of the main electronics (not attributable to external sensors). Check after reset, measure voltages and connectors; if it reappears, replace the PCB. |
