| Fault Code / Fault Image | System Behaviour |
| 1 | Flame lockout after several ignition attempts |
| 2 | False flame |
| 3 | High water temperature limit |
| 5 | No tacho from fan |
| 8 | Flame circuit error |
| 9 | Valve driver circuit error |
| 11 | Flow/return sensor calibration error |
| 12 | Default lockout |
| 13 | Elapsed the number of retrials |
| 21 | ADC error |
| 26 | Flame signal lost 5 times in 4 minutes |
| 31 | Centra heating supply sensor error (open or short) |
| 44 | Central heating rerturn sensor error (open or short) |
| 7 | High flue gas tempurature |
| 25 | CRC error |
| 30 | Boiler flow temprature sensor short circuit |
| 31 | Boiler flow temperature sensor open ciruit |
| 32 | Domestic hot water temperature sensor short circuit |
| 33 | Domestic hot water temperature sensor open circuit |
| 34 | Low mains supply voltage |
| 37 | Low system water pressure |
| 40 | High system water pressure |
| 41 | No water pressure signal recievced fom MMI |
| 45 | Flue gas temperature sensor short circuit |
| 46 | Flue gas temperature sensor open circut |
| 47 | Water pressure sensor open circuit |
| 99 | Communication MMI -ESYS lost |
| E01 | Ignition lockout |
| E02 | False flame lockout |
| E03 | Overheat lockout |
| E05 | Fan fault |
| E08 | Flame circuit failure |
| E09 | Valve feed back error |
| E12 | EEPROM lockout |
| E15 | Sensor drift lockout |
| E16, E17, E18 | Sensor stuck lockout |
| E21 | ADC lockout |
| E33 | Return thermistor fault |
| E34 | Low power supply lockout |
| E35 | Flow thermistor fault |
| F07 | Exhaust sensor fault |
| F13 | Remote reset lockout |
| F37 | Low water pressure |
| F40 | Water pressure too high |
| F47 | Water pressure sensor not connected |
| F52 | Domestic hot water (DHW) sensor fault |
| F53 | Flue temperature sensor lockout |
