| Code | Meaning |
|---|---|
| C0 | Boiler chip card (BCC) activation fault |
| C2 | Boiler chip card (BCC) fault |
| F1 | Low water pressure |
| F2 | Flame loss |
| F3 | Fan fault |
| F4 | Flow thermistor |
| F5 | Return thermistor |
| F6 | Outside sensor failure |
| F7 | Low mains voltage |
| F9 | Unconfigured printed circuit board (PCB) |
| L1 | Flow temperature overheat or no water flow |
| L2 | Flame loss |
| L5 | 5 boiler resets in 15 minutes |
| L6 | False flame lockout |
Gas work stays with a Gas Safe registered engineer. Some codes only apply to a named range — check the model column.