Use this tool 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 30

Boiler mode
System behaviour
Diagnosis
Vitocontrol-S, with Vitotronic 100 / Vitocrossal 300 / Vitodens 200-W / 222-F / Vitotronic 100 / 200 / 300
Burner is started and stopped via an adjustable high limit
Short circuit – Boiler water temperature sensor
Vitocontrol-S with Vitotronic 100 / Vitodens 100-W (CombiPLUS)/ 200-1
Burner blocked
Boiler water temperature sensor shorted out

Fault Code B3 and E5

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Constant mode
Invalid hardware recognised

Fault Code A0, A1, A2, AA, and AC

Boiler mode
System behaviour
Diagnosis
Vitodens 200
Pump runs at maximum speed
Open circuit – BUS connection with variable speed heating circuit pump

Fault Code FA and FB

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Control Mode
Communication fault

Fault Code A8

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Control mode
Communication fault, Programming unit

Fault Code E4

Boiler mode
System behaviour
Diagnosis
Vitocontrol-S with Vitotronic 100 / Vitocrossal 300 / Vitodens 200-W / 222-F / Vitotronic 300
Burner in fault mode
At burner start, flame signal is missing or too weak

Fault Code B1

Boiler mode
System behaviour
Diagnosis
Vitocontrol-S with Vitotronic 100 / Vitotronic 100 / 200 / 300 / Vitotronic 300-K with Vitotronic 100
Emissions test mode
Internal electronics fault
Vitocontrol-S with Vitotronic 100 / Vitodens 200-W
Regulates as if the outside temperature was 32°F (0°C)
Internal fault
Vitotronic 050/200-H
Undefined control characteristics
Internal electronics fault

Fault Code 28

Boiler mode
System behaviour
Diagnosis
Vitocontrol-S with Vitotronic 100
Vitocontrol-S, VD2/CT3/CM2 controls in a stand-alone manner w/o supply temperature sensor (supply temperature may not be high enough)
Open circuit – Common supply temperature sensor
Vitocontrol-S with Vitotronic 100 / Vitotronic 300-K,with Vitotronic 100
Vitocontrol-S, WB2B controls in a stand-alone manner w/o supply temperature sensor (supply temperature may not be high enough)
Common supply temperature sensor cable broken
Vitocrossal 300 / Vitodens 200-W / 22-F
Regulates without supply temperature sensor (low-loss header)
System supply temperature sensor cable broken
Vitotronic 050/200-H
Mixing valve closes
Cable break – Supply temperature sensor
Vitotronic 050/200-H
Mixing valve is closed
Open circuit – Supply temperature sensor of mixing valve circuit M1
Vitotronic 200-H / Vitotronic 200 / 300
Mixing valve is being closed
Lead break, Supply temperature sensor, heating circuit with mixing valve M1 (heating circuit 1)
Vitotronic 300 Vitotronic / 300-K with Vitotronic 300 / 200
Stand-alone control unit without supply temperature sensor (possibly supply temperature not high enough)
Lead break, Common supply temperature sensor
Vitotronic 300-K with Vitotronic 100
Vitotronic 300-K, MW1S controls in a stand-alone manner w/o strap-on sensor (supply temperature may not be high enough)
Open circuit – Strap-on temperature sensor

Fault Code A3, B0, F1, F-E1 and F-E2

Boiler mode
System behaviour
Diagnosis
Vitocrossal 300 / Vitodens 200-W / 222-F / 300
Control mode (stays in factory default setting)
Faulty Programming unit

Fault Code 0b

Boiler mode
System behaviour
Diagnosis

Fault Code 29, 41, 49, F80, F81, F83, F88 and F89

Boiler mode
System behaviour
Diagnosis
Vitotronic 200 / 300
Normal operation without influence of return water temperature
Open circuit 1 or 2 – Return water temperature sensor (of mixing valve circuit 1)

Fault Code E1, E7, E8, E9, EA, EB, EC and FF2

Boiler mode
System behaviour
Diagnosis
Vitodens 200-W / 222-F / Vitotronic 300
Burner in fault mode
Heating water flow rate too low during calibration; flow switch caused shutdown

Fault Code 0F

Boiler mode
System behaviour
Diagnosis
Vitodens 222-F
Control mode
Code ”0F” is only displayed in the fault history(service required)
Vitotronic 300 / Vitotronic 300-K, with Vitotronic 300 / Vitodens 200-W / Vitocontrol-S, with Vitotronic 100
Control mode / Controlled operation
Service required. ”0F” is only displayed in the fault history.
Vitotronic 200 / 300
Normal operation
Service required
Vitocontrol-S, MW1 with Vitotronic 100 / Vitotronic 300-K, MW1S with Vitotronic 100
Control mode
Maintenance ”0F” is only displayed in the fault history

Fault Code 90, 91, 92, 93, 94, 98, 99, 9A, 9B , 9C, 9E, 9F and AB

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Control mode
Short circuit – Temperature sensor [5] / [6] / [7] / [10]

Fault Code C9, CA and CB

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Boiler drives up to electronic maximum limit
Boiler does not log in at the cascade control unit

Fault Code A7

Boiler mode
System behaviour
Diagnosis
Vitocontrol-S with Vitotronic 100 / Vitotronic 100 / Vitotronic 300-K with Vitotronic 300
Control mode
Isolation valve configuration fault: Coding OC:2, OC:3 or OC:4 set, and coding 4E:1 not set

Fault Code 38

Boiler mode
System behaviour
Diagnosis
Vitodens – 200-W / 222-F / COMBIPLUS
Burner blocked
Boiler water temperature sensor cable broken
Vitotronic 100 / 200 / 300 / Vitocontrol-S with Vitotronic 100
Burner is switched on and off by the adjustable high limit
Open circuit – Boiler temperature sensor
Vitotronic 300-K with Vitotronic 300 / Vitotronic 300-K with Vitotronic 300
The burner is started and stopped via a temperature controller
Lead break, Boiler water temperature sensor
Vitodens 100-W
Burner blocked
Boiler water temperature sensor lead broken

Fault Code 5A, B7, and B8

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Control mode
Lead break, low-loss header Supply temperature sensor
All Viessmann boilers
Burner blocked / control mode
sensor cable broken

Fault Code 52

Boiler mode
System behaviour
Diagnosis
Vitotronic 300
Control mode
Short circuit – Supply temperature sensor low-loss header
Vitodens 100-W CombiPLUS
Burner blocked (with CombiPLUS only)
Flow sensor shorted out (in CombiPLUS)

Fault Code CC and F0

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Burner in fault mode
Ionisation current too high during calibration Boiler temperature limiter responded(F2) air or blockage in system/pump failure

Fault Code B6

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Control mode
Open circuit – KM BUS to solar control unit / Extension AM1 / DE1-DE3 M1 / communication fault

Fault Code 0b

Boiler mode
System behaviour
Diagnosis

Fault Code D5

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Burner blocked
Flue gas temperature sensor not properly positioned / Check Sensor External pump fitted on the system(100-w) A-3 fault.

Fault Code 8C, 8D, 8E and 8F

Boiler mode
System behaviour
Diagnosis
Vitotronic 300
Burner control unit in a fault state
Lead break, Boiler water temperature sensor, burner control unit

Fault Code 60, 68, 70, 78, BD, BE and BF

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
– No output reduction – Return control open – Boiler with maximum temperature
Short/open circuit – Temperature sensor [17A]

Fault Code F-FA, F-FB and FR

Boiler mode
System behaviour
Diagnosis
Vitocrossal 200 / 400-620 / 186-311
Fan runs without demand; Burner control unit in a fault state
Fan has not stopped; cable [100A] faulty; fan faulty; burner control unit faulty

Fault Code E2 and E3

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Burner blocked
Fault, supply voltage 24V

Fault Code 40 and 44

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Mixing valve closes
Heating circuit 2 with mixing valve supply short circuit on temperature sensor

Fault Code 48 and 4C

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Mixing valve closes / Closed
Heating circuit 2 with mixing valve supply temperature sensor cable broken / open circuit

Fault Code A9, BA, BB, BC and FE0

Boiler mode
System behaviour
Diagnosis
Vitodens 200
Boiler cools down
Sensor inputs are not read correctly

Fault Code 50, 51, 58 and 59

Boiler mode
System behaviour
Diagnosis
Vitodens 200-W / 222-F
No DHW heating/ Fault with DHW
Short circuit/open circuit – DHW tank temperature sensor or lead break

Fault Code F-B7, F-F4, F-F2, F-F7, F-F8 and F-F9

Boiler mode
System behaviour
Diagnosis
Vitocrossal 200
Case A: Burner control unit in a fault state; system cools down; burner control unit locked out. Case B: Type of coding card
Case A: Coding card not inserted in the burner control unit; incorrect or faulty coding card. Case B: Coding card does not match burner control unit.

Fault Code 10, 14, F3, and F4

Boiler mode
System behaviour
Diagnosis
Vitodens 200
Burner control switches to lockout
No flame signal is present

Fault Code FE4

Boiler mode
System behaviour
Diagnosis
Vitocrossal 200
Burner shuts down
Multiple detection of undervoltage

Fault Code FC

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Burner in fault mode
Gas valve faulty or faulty modulation valve control; or vent system blocked. Check fan, fan cable, PCB

Fault Code EE and EF

Boiler mode
System behaviour
Diagnosis
Vitodens 100-W / 200 / 0 / Vitotronic 300
Burner blocked
Faulty Air pressure switch. Air damper(flap)stuck

Fault Code 55, 56 and 57

Boiler mode
System behaviour
Diagnosis
Vitotronic 300-K, with Vitotronic 200
Control mode
Maintenance or fault on Vitotronic 100 of boiler 5-8

Fault Code 20

Boiler mode
System behaviour
Diagnosis
Vitocontrol-S with Vitotronic 100 / Vitotronic 300 / 300-K / 200 / 100
Stand-alone control unit without supply temperature sensor (possibly supply temperature not high enough)
short circuit – Common supply temperature sensor
Vitocontrol-S with Vitotronic 100 / Vitotronic 300-K, with Vitotronic 200
Vitocontrol-S, controls in a stand-alone manner w/o supply temperature sensor (supply temperature may not be high enough)
Common supply temperature sensor shorted out
Vitocrossal 300
Regulates without supply temperature sensor (low-loss header)
Short circuit – System Flow temperature sensor
Vitodens 200-W / 222-F
Regulates without supply temperature sensor (low-loss header)
Short circuit – System supply temperature sensor
Vitotronic 050/200-H< / 200 / 200-H / 300
Mixing valve closes/ closed
Short circuit – Supply temperature sensor / mixing valve circuit M1
Vitotronic 300-K, with Vitotronic 100
Vitotronic 300-K, MW1S controls in a stand-alone manner w/o strap-on sensor (supply temperature may not be high enough)
Short circuit – Strap-on temperature sensor
Vitodens 200-W
Regulates without supply temperature sensor (low-loss header)
System supply temperature sensor shorted out

Fault Code FE

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Burner blocked or in fault mode
Strong interference (EMC) field nearby, or Faulty main PCB

Fault Code 0b

Boiler mode
System behaviour
Diagnosis
Vitodens 200
The burner control switches to lockout. The fan does not idle after auto reset (incorrect fan rpm).
Severe wind conditions in the vent system
Vitodens 100-W
Burner blocked
Insufficient water flow. Incorrect flow direction. Defective flow switch.(Blockage)

Fault Code 21

Boiler mode
System behaviour
Diagnosis
Vitotronic 200 / 300
operation without influence of return water temperature
Short circuit – Return water temperature sensor

Fault Code B2

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Control mode
Internal electronics fault

Fault Code 19

Boiler mode
System behaviour
Diagnosis
Vitotronic 300
Activates after 0°C / 32°F outdoor temperature
Communication fault, Wireless Outdoor temperature sensor

Fault Code B5

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Control Mode
External safety equipment

Fault Code 80, 81, 82, 83 and FD

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Burner control unit in a fault state; system cools down; burner control unit locked out
Short circuit – Boiler water temperature sensor, burner control unit

Fault Code B4

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Normal operation / fault around burner control unit
Internal fault (PCB)

Fault Code C2-C8, CD-CF, D2-D8, DA-DF, and E0

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Boiler cools down
Fixed high limit has responded or fuse F2 has blown.

Fault Code F5

Boiler mode
System behaviour
Diagnosis
All Viessmann boilers
Gas pressure switch shows no gas pressure / Electrical connection fault
Gas shut-off valve closed; gas pressure switch faulty; multiple problems with gas supply

Fault Code AD

Boiler mode
System behaviour
Diagnosis
Vitodens 200
Setting via service level not possible
Data points are not stored; internal fault VR20

Fault Code 88, 89, and E6

Boiler mode
System behaviour
Diagnosis
Vitocontrol-S with Vitotronic 100 / Vitotronic 300-K with Vitotronic 100 / 200
Control mode
Communication fault, Vitotronic 100 of boiler 1-4

Fault Code 41

Boiler mode
System behaviour
Diagnosis
Vitotronic 300
Operation without accounting for return water temperature
Short circuit – Return water temperature sensor of mixing valve circuit 2

Fault Code B9, ED, F0, F-E5, F-EC, F-ED, F-EE, F-EF, F-FD and F-FF

Boiler mode
System behaviour
Diagnosis
Vitocontrol-S with Vitotronic 100 / Vitotronic 100 / 300 / Vitotronic 300-K with Vitotronic 300
Boiler cools down
fault: Maximum pressure limiter 1 2

Fault Code C1

Boiler mode
System behaviour
Diagnosis
Vitodens 200
Burner control unit switches to lockout (due to large line voltage fluctuations)
Differential air pressure sensor / open circuit

Fault Code 0C

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

Fault Code A4

Boiler mode
System behaviour
Diagnosis
Vitodens 222-F
Burner blocked. The venting program is started automatically
Air lock in the Internal circulation pump or minimum flow rate not achieved

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 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 equipment
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 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 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 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

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