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 modeSystem behaviourDiagnosis
Vitotronic 300-K with Vitotronic 200Control modeCommunication fault, Vitotronic 100 of boiler 5-8

Fault Code 10

Boiler modeSystem behaviourDiagnosis
Vitodens 200-W / 222-F / Vitotronic 300 / 200/ 200-H / 050/200-H / 300-K / vitocontrol-SBoiler operates based on outdoor temperature of 32°F / 0°CShort circuit – Outdoor temperature sensor
Vitotronic 300-K, MW2S with Vitotronic 100 / Vitodens 100-W (combiPLUS) / 200-w / Vitocontrol-S, WB2B with Vitotronic 100Controls as if the outdoor temperature / Constant ModeOutdoor temperature sensor shorted out

Fault Code F6, 58, F9, F-E1, F-E2 and F-F6

Boiler modeSystem behaviourDiagnosis
All Viessmann boilersBurner in fault mode / Emergency operationFan not at standstill / plug-in connection

Fault Code D4

Boiler modeSystem behaviourDiagnosis
Vitotronic 300 / Vitotronic 300-K with Vitotronic 300Boiler cools downFault, safety equipment at ” X2 / X3 / X7″ of plug-in adaptor 2 for external safety equipmentFan not at standstill / plug-in connection
Vitodens 200Boiler operates in emergency mode (after approx. 30 min. BUS fault) OR Boiler cools downInternal BUS fault OR Open circuit – Internal BUS connection

Fault Code 18 and D1

Boiler modeSystem behaviourDiagnosis
Vitodens 100 / 200-W / 222-F / Vitotronic 300-K With 100 / Vitocontrol-SBoiler operates based on outdoor temperature of 32°F / 0°C / Constant ModeOutdoor temperature sensor cable broken
Vitotronic / 100 / 200 / 300 / 050/200-H /300-K / Vitocontrol-S, MW1 with Vitotronic 100Operates on basis of 32°F / 0°C outdoor temperatureOpen circuit – Outdoor temperature sensor
Vitotronic 200-H / Vitotronic 300-K, MW1B with Vitotronic 300 / Vitotronic 300-K, MW2B with Vitotronic 200Controls as if the outdoor temperatureLead break, Outdoor temperature sensor
Vitotronic 050/200-HActivates after 0°C / 32°F outdoor temperatureCable break – Outdoor temperature sensor
Vitodens 100-WBurner in fault modeDIP switch S2 is set to “ON”

Fault Code A4

Boiler modeSystem behaviourDiagnosis
Vitodens 222FBurner blocked. The venting program is started automaticallyAir lock in the Internal circulation pump or minimum flow rate not achieved

Fault Code OC

Boiler modeSystem behaviourDiagnosis
Vitodens 100-WBurner blockedInsufficient power supply
Vitodens 200Burner control switches to lockoutFlame signal still present after switching off