Fault Codes
Use this page to diagnose a fault code on your Viessmann boiler. Please be aware that the diagnosis for the code appearing may differ depending on the boiler. In order to correctly diagnose the fault your Viessmann boiler is experiencing or if you cannot find your error code, we recommend contacting a Viessmann Trained Installer.
Fault Code 5C, 5D, 5E and 5F
| Boiler mode | System behaviour | Diagnosis |
| Vitotronic 300-K with Vitotronic 200 | Control mode | Communication fault, Vitotronic 100 of boiler 5-8 |
Fault Code 10
| Boiler mode | System behaviour | Diagnosis |
| Vitodens 200-W / 222-F / Vitotronic 300 / 200/ 200-H / 050/200-H / 300-K / vitocontrol-S | Boiler operates based on outdoor temperature of 32°F / 0°C | Short circuit – Outdoor temperature sensor |
| Vitotronic 300-K, MW2S with Vitotronic 100 / Vitodens 100-W (combiPLUS) / 200-w / Vitocontrol-S, WB2B with Vitotronic 100 | Controls as if the outdoor temperature / Constant Mode | Outdoor temperature sensor shorted out |
Fault Code F6, 58, F9, F-E1, F-E2 and F-F6
| Boiler mode | System behaviour | Diagnosis |
| All Viessmann boilers | Burner in fault mode / Emergency operation | Fan not at standstill / plug-in connection |
Fault Code D4
| Boiler mode | System behaviour | Diagnosis |
| Vitotronic 300 / Vitotronic 300-K with Vitotronic 300 | Boiler cools down | Fault, safety equipment at ” X2 / X3 / X7″ of plug-in adaptor 2 for external safety equipmentFan not at standstill / plug-in connection |
| Vitodens 200 | Boiler operates in emergency mode (after approx. 30 min. BUS fault) OR Boiler cools down | Internal BUS fault OR Open circuit – Internal BUS connection |
Fault Code 18 and D1
| Boiler mode | System behaviour | Diagnosis |
| Vitodens 100 / 200-W / 222-F / Vitotronic 300-K With 100 / Vitocontrol-S | Boiler operates based on outdoor temperature of 32°F / 0°C / Constant Mode | Outdoor temperature sensor cable broken |
| Vitotronic / 100 / 200 / 300 / 050/200-H /300-K / Vitocontrol-S, MW1 with Vitotronic 100 | Operates on basis of 32°F / 0°C outdoor temperature | Open circuit – Outdoor temperature sensor |
| Vitotronic 200-H / Vitotronic 300-K, MW1B with Vitotronic 300 / Vitotronic 300-K, MW2B with Vitotronic 200 | Controls as if the outdoor temperature | Lead break, Outdoor temperature sensor |
| Vitotronic 050/200-H | Activates after 0°C / 32°F outdoor temperature | Cable break – Outdoor temperature sensor |
| Vitodens 100-W | Burner in fault mode | DIP switch S2 is set to “ON” |
Fault Code A4
| Boiler mode | System behaviour | Diagnosis |
| Vitodens 222F | Burner blocked. The venting program is started automatically | Air lock in the Internal circulation pump or minimum flow rate not achieved |
Fault Code OC
| Boiler mode | System behaviour | Diagnosis |
| Vitodens 100-W | Burner blocked | Insufficient power supply |
| Vitodens 200 | Burner control switches to lockout | Flame signal still present after switching off |