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2024 Viessmann Boiler Error & Fault Codes


Viessmann boilers have an inbuilt error code/fault display function known as the 'Fault Code Display'. Fault Code Display's purpose is to clearly communicate to the user what has caused the issue within the boiler. All you have to do is identify which error code has been displayed on your boiler's LCD display.

This page lists all the fault codes that occur on Viessmann boilers, and what the error might mean. It is intended as a reference to help you quickly identify issues so that you can contact an engineer. We strongly recommend that you do not attempt to repair your boiler yourself; always contact a Gas Safe registered engineer who is qualified to work with boilers.

My boiler's not working and not showing an error code?

If your boiler is not displaying a fault code, then there might be an issue with the water and gas supplies. Check whether you have credit on your prepayment meter and if there is good supply of water, gas, and electricity at your property.

The display on your boiler may fail to show any information. This could be because the boiler is on a separate electricity circuit which is not providing power to your boiler.

Complete list of Viessmann boiler fault codes

Fault Code Model(s) Affected Behaviour Potential Cause
0AVitodens 200The controls switch to lockoutThe fan speed is faulty
0BVitodens 100-WBlocked burnerFlow direction incorrect

Water flow insufficient

Flow switch is defective
0BVitodens 200The fan RPM is not correct and it doesn't idle after reset

The burner control switches to lockout
The vent system has been effected by severe wind conditions
0CVitodens 100-WBlocked burnerThe power supply is insufficient
0CVitodens 200The burner control switches to lockoutAfter switching off the flame signal was still present
0DVitodens 200The controls switch to lockoutwhilst the burner is active or the reset button has been pressed repeatedly
0FVitotronic 100, 300-K with MW1 & MW1S

Vitocontrol-S
Control modeMaintenance, displayed in the fault history
0FVitotronic 100, 300, 330-K

Vitodens 200-W

Vitocontrol-S
Controlled operation / modeService is required
0FVitodens 222-FControl modeDisplayed in the fault history
0FVitotronic 200, 300Operation normalService is required
1A, 1BVitodens 200Blocked burnerFaulty flow sensor
1FVitodens 200Blocked burnerThe flow rate is too large
02Vitodens 200The controls switch to lockoutActivated safety chain
04, 05, 06, 08Vitodens 200The controls switch to lockoutThe speed of the fan is too high or low at the start
5A, B7, B8All Viessmann boilersControl modeSupply temperature sensor

Lead break

Low loss header
5A, B7, B8All Viessmann boilersControl mode

Blocked burner
Broken cable sensor
5C, 5D, 5E, 5FVitotronic 300-K, 200Control modeCommunication fault
07, 09Vitodens 200The controls switch to lockoutWhilst in standby mode the basic level of air pressure isn't correct
8C, 8D, 8E, 8FVitocontrol-S

Vitotronic 100, 200, 300-K
Control modeCommunication fault
10Vitodens 200-W, 222-F

Vitotronic 300-K, 300, 200, 200-H, 050/200-H

Vitocontrol-S
Operation based on the outdoor temperature of 0CThe outdoor temperature sensor has short circuited
10Vitotronic 300-K, MW2S with 100, WB2B with 100

Vitodens 100-W (combiPLUS) / 200-W

Vitocontrol-S
Constant mode

Outdoor temperature controls
The outdoor temperature sensor has shorted out
10, 14, F3, F4Vitodens 200Burner control in lockoutNo present flame signal
18, D1Vitodens 100, 200-W, 222-F

Vitotronic 300-K with 100

Vitocontrol-S
Operation based on the outdoor temperature of 0C

Constant Mode
Sensor cable broken for outdoor tempearture
18, D1Vitotronic 100, 200, 300, 050-200-H, 300-K, MW1 with 100

Vitocontrol-S
Operation based on the outdoor temperature of 0COutdoor temperature sensor has open circuit
18, D1Vitotronic 200-H, 300-K, MW1B with 300 / 300-K, MW2B with 200Controls as if outdoor temperatureOutdoor temperature sensor or lead break
18, D1Vitotronic 050/200-HWhen outdoor temperature is 0C it activatesCable break on the outdoor temperature sensor
18, D1Vitodens 100-WFault in burnerThe DIP switch S2 is on
19Vitotronic 300Operation based on the outdoor temperature of 0CWireless outdoor temperature sensor

Fault with communication
20Vitocontrol-S with Vitotronic 100

Vitotronic 200, 300-K
Supply temperature may not be high enough

Vitocontrol-S controls in a stand alone manner without supply temperature sensor
Temperature sensor has shorted out
20Vitodens 200-W, 222-FLow loss header

Temperature sensor regulates without supply
System supply temperature sensor has short circuited
20Vitocontrol-S with Vitotronic 100

Vitotronic 100, 200, 300, 300-K
Supply temperature may not be high enough

There is no supply temperature sensor for the stand-alone control unit
The common supply temperature sensor has short circuited
20Vitotronic 100, 300-KSupply temperature may not be high enough

MW1S controls in a stand-alone manner without strap-on sensor
The strap-on temperature sensor has short circuited
20Vitocrossal 300Low loss header

Temperature sensor regulates without supply
System flow temperature sensor has short circuited
20Vitotronic 050/200-H, 200, 200-H, 300Mixing valve closedSupply temperature sensor has short circuited

Mixing valve circuit M1
20Vitodens 200-WLow loss header

Temperature sensor regulates without supply
The system supply temperature sensor has shorted out
21Vitotronic 200, 300Return water temperature operation without influenceReturn water temperature sensor short circuited
25Vitodens 200There is a high boiler water temperature whilst the boiler is in operationFor 30 minutes or over the emissions test switch has turned to the hand symbol
26Vitodens 200Continuous relay test when the boiler is in operationFor 30 minutes the setting mode for minimum or maximum rated input has been active
28Vitotronic 050/200HMixing valve is closedOpen circuit on the supply temperature sensor of the mixing valve circuit M1
28Vitocrossal 300

Vitodens 200-W, 222-F
Low loss header

Regulates without supply temperature sensor
Cable broken on the system supply temperature sensor
28Vitotronic 050/200HMixing valve closesCable broken on the supply temperature sensor
28Vitotronic 300, 300-KStand-alone control unit without supply temperature sensor

The temperature may not be high enough
Common supply temperature sensor, lead break
28Vitotronic 100, 300-KVitotronic 300-K & MW1S controls in a stand alone manner without strap-on sensor

The temperature may not be high enough
Strap-on temperature sensor has an open circuit
28Vitocontrol-S

Vitotronic 100, 300-K
Vitocontrol-S & WB2B controls in a stand alone manner without supply temperature sensor

The temperature may not be high enough
Cable broken on the common supply temperature sensor
28Vitotronic 100

Vitocontrol-S
Vitocontrol-S, VD2, CT3, CM2 controls in a stand alone manner without temperature sensor

The temperature may not be high enough
Common supply temperature sensor has an open circuit
28Vitotronic 200, 200-H, 300Mixing valve is in the process of being closedHeating circuit with mixing valve M1

Lead break

Supply temperature sensor
29, 41, 49, F80, F81, F83, F88 and F89Vitotronic 200, 300No influence of return water temperature and normal operationReturn water temperature sensor has an open circuit 1 or 2
30Vitocontrol-S

Vitoronic 100, 200, 300

Vitodens 200-W, 222-F

Vitocrossal 300
The burner is started and stopped via adjustable high limitWater temperature sensor has short circuited
30Vitocontrol-S

Vitotronic 100

Vitodens 100-W (CombiPLUS), 200-1
Blocked burnerThe water temperature sensor shorted out
35Vitodens 200The boiler doesn't activateThe reset button has been pressed, whilst the burner is off, but the emissions test switch is turned to the hand symbol
38Vitodens 100-WBlocked burnerWater temperature sensor lead broken
38Vitotronic 300-K, 300Temperature controller starts and stops the burnerWater temperature sensor

Lead break
38Vitodens 200-W, 222-F, CombiPLUSBlocked burnerCable broken on water temperature sensor
38Vitotronic 100, 200, 300

Vitocontrol-S
Burner switched on and off by the adjustable high limitTemperature sensor has an open circuit
40, 44All Viessmann boilersMixing valve closesHeating circuit 2 with mixing valve supply short circuit on temperature sensor
48, 4CAll Viessmann boilersMixing valve is closing or has closedCable broken on mixing valve supply temperature sensor, it has an open circuit (Heating circuit 2)
50, 51, 58, 59Vitodens 200-W, 222-FFault with DHW

No DHW heating
DHW tank temperature sensor or lead break has short circuited or an open circuit
52Vitotronic 300Control modeLow loss header with temperature sensor supply which has short circuited
52Vitodens 100-W CombiPLUSBlocked burnerShorted out flow sensor
55, 56, 57Vitotronic 300-K, 200Control modeMaintenance or error
60, 68, 70, 78, BD, BE, BFAll Viessmann boilersNo output reduction

Open return control

Maximum temperature
Temperature sensor has short circuited or an open circuit
80, 81, 82, 83, FDAll Viessmann boilersFault state in burner control unit

System cools down

Burner control unit locked out
Water temperature sensor or burner control unit has short circuited
88, 89, E6Vitotronic 300Fault state with the burner control unitBurner control unit

Water temperature sensor

Lead break
90, 91, 92, 93, 94, 98, 99, 9A, 9B , 9C, 9E, 9F, ABAll Viessmann boilersControl modeTemperature sensor has short circuited
A0, A1, A2, AA, ACVitotronic 300, 300-KThe boiler cools downFault with the safety equipment at X2, X3, X7 of plugin adaptor 2
A0, A1, A2, AA, ACVitodens 200BUS fault: Boiler operates in emergency mode or the boiler cools downBUS fault or open circuit on internal BUS connection
A2Vitodens 200N/AFault with the KM-BUS
A3, B0, F1, FE1, FE2All Viessmann boilersBlocked burnerCheck flue gas temperature centre, it may not be properly positioned
A4Vitodens 200Maximum speed reached for pumpOpen circuit in BUS connection with variable speed heating circuit pump
A5Vitodens 200N/AShort or open circuit
A7Vitocrossal 300

Vitodens 200-W, 222-F, 300
Factory default control modeProgramming unit faulty
A8Vitodens 222-FBlocked burner, automatically started venting programMinimum flow rate has not been achieved or air lock in internal circulation pump
A9, BA, BB, BC, FE0All Viessmann boilersControl modeCommunication error
ADVitocontrol-S

Vitotronic 100, 300, 300-K
Control modeConfiguration error with isolation valve (OC:2, OC:3, OC:4 set), (4E:1 not set)
B1All Viessmann boilersControl modeCommunication error with programming unit
B2Vitodens 200Boiler cools downSensor inputs are not being read correctly
B3, E5Vitodens 200Not possible to set via service levelInternal fault, data points not stored (VR20)
B4Vitotronic 050/200-HControl characteristics undefinedFault with internal electronics
B4Vitocontrol-S

Vitotronic 100

Vitodens 200-W
Regulates as if outside temperature was at 0CFault interally
B4Vitocontrol-S

Vitotronic 100, 200, 300, 300-K
Emissions test modeFault with internal electronics
B5All Viessmann boilersControl modeFault with internal electronics
B6All Viessmann boilersConstant modeRecognisation of invalid hardware
B9, ED, F0, FE5, FEC, FED, FEE, FEF, FFD, FFFAll Viessmann boilersFault of boiler control unit

Normal operation
Fault interally
C1All Viessmann boilersControl modeExternal safety equipment
C2-C8, CD-CF, D2-D8, DA-DF, E0All Viessmann boilersControl modeOpen circuit on KM BUS to solar control unit

AM1 Extension

DE-DE3 M1

Communication fault
C9, CA, CBVitocontrol-S

Vitotronic 100, 300, 300-K
Boiler cools downMaximum pressure limited error
CC, F0Vitodens 200Large voltage fluctuations means the burner control unit switches to lockoutDifferential air pressure sensor or open circuit
D4All Viessmann boilersBoiler cools downFuse F2 has blown or fixed high limit has responded
D5All Viessmann boilersBoiler drives up to electronic maximum limitThe boiler is not logging in at the cascade control unit
E1, E7, E8, E9, EA, EB, EC, FF2All Viessmann boilersFault mode in relation to burnerDuring calibration ionization is too high
E2, E3Vitodens 200-W, 222-F

Vitotronic 300
Fault mode in relation to burnerWater flow rate too low during calibration

Flow switch has caused shutdown
E4All Viessmann boilersBlocked burnerVoltage supply faulty (24V)
EE, EFVitocontrol-S

Vitotronic 100, 300

Vitodens 200-W, 222-F

Vitocrossal 300
Fault mode in relation to burnerWhen the burner starts the flame signal is too weak or missing
F5Vitodens 100-W, 200, 300

Vitotronic 300
Blocked burnerAir pressure switch faulty
F6, 58, F9, FE1, FE2, FF6All Viessmann boilersGas pressure switch is showing there is no gas pressure or electrical connection faultGas valve shut off

Faulty gas pressure switch

Multiple issues with gas supply
FA, FBAll Viessmann boilersFault mode in relation to burner

Emergency operation
Plug-in connection

Fan not at standstill
FB7, FF4, FF2, FF7, FF8, FF9Vitocrossal 200Fault state with furner control unit, system cools down, lockout of burner control unit

Type of coding card
Coding card not correctly inserted into burner control unit, or faulty card

Coding card doesn't match burner control unit
FCAll Viessmann boilersFault mode in relation to burnerFaulty gas valve

Faulty modulation valve control

Vent system blocked
FEAll Viessmann boilersFault mode in relation to burnerFaulty main printed circuit board

Strong interference field nearby
FE4Vitocrossal 200Burner has shut downUnder set voltage detected multiple times
FFA, FFB, FRVitocrossal 200, 400-620, 186-311Fault mode in relation to burner

Fan runs without demand
Fan has not stopped

Faulty 100A cable

Faulty fan

Fault with burner control unit
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Table of Contents


  1. All Error Codes

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