Viessmann Boiler Fault & Error Codes

Has your Viessmann boiler produced an error code? If that is the case, although this can appear a daunting prospect, don't worry, there may be a quick solution.

On this page you can find a list of all the Viessmann boiler fault codes and the models that it applies too. Each of these codes has a potential cause which should help you get to the bottom of what the issue is. If you are stuck and can't find the issue then our expert boiler engineer partners may be able to help, simply fill out the quick form above and they will be in contact to try and help you find a solution.

General Faults & Errors

This section is an overview of all of the types of errors that can occur on a Viessmann boilers.

Fault CodeBehaviourPotential CauseModel(s) Affected
0AThe controls switch to lockoutThe fan speed is faultyVitodens 200
0BBlocked burnerFlow direction incorrect

Water flow insufficient

Flow switch is defective
Vitodens 100-W
0BThe 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 conditionsVitodens 200
0CBlocked burnerThe power supply is insufficientVitodens 100-W
0CThe burner control switches to lockoutAfter switching off the flame signal was still presentVitodens 200
0DThe controls switch to lockoutwhilst the burner is active or the reset button has been pressed repeatedlyVitodens 200
0FControl modeMaintenance, displayed in the fault historyVitotronic 100, 300-K with MW1 & MW1S

Vitocontrol-S
0FControlled operation / modeService is requiredVitotronic 100, 300, 330-K

Vitodens 200-W

Vitocontrol-S
0FControl modeDisplayed in the fault historyVitodens 222-F
0FOperation normalService is requiredVitotronic 200, 300
1A, 1BBlocked burnerFaulty flow sensorVitodens 200
1FBlocked burnerThe flow rate is too largeVitodens 200
02The controls switch to lockoutActivated safety chainVitodens 200
04, 05, 06, 08The controls switch to lockoutThe speed of the fan is too high or low at the startVitodens 200
5A, B7, B8Control modeSupply temperature sensor

Lead break

Low loss header
All Viessmann boilers
5A, B7, B8Control mode

Blocked burner
Broken cable sensorAll Viessmann boilers
5C, 5D, 5E, 5FControl modeCommunication faultVitotronic 300-K, 200
07, 09The controls switch to lockoutWhilst in standby mode the basic level of air pressure isn't correctVitodens 200
8C, 8D, 8E, 8FControl modeCommunication faultVitocontrol-S

Vitotronic 100, 200, 300-K
10Operation based on the outdoor temperature of 0CThe outdoor temperature sensor has short circuitedVitodens 200-W, 222-F

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

Vitocontrol-S
10Constant mode

Outdoor temperature controls
The outdoor temperature sensor has shorted outVitotronic 300-K, MW2S with 100, WB2B with 100

Vitodens 100-W (combiPLUS) / 200-W

Vitocontrol-S
10, 14, F3, F4Burner control in lockoutNo present flame signalVitodens 200
18, D1Operation based on the outdoor temperature of 0C

Constant Mode
Sensor cable broken for outdoor tempeartureVitodens 100, 200-W, 222-F

Vitotronic 300-K with 100

Vitocontrol-S
18, D1Operation based on the outdoor temperature of 0COutdoor temperature sensor has open circuitVitotronic 100, 200, 300, 050-200-H, 300-K, MW1 with 100

Vitocontrol-S
18, D1Controls as if outdoor temperatureOutdoor temperature sensor or lead breakVitotronic 200-H, 300-K, MW1B with 300 / 300-K, MW2B with 200
18, D1When outdoor temperature is 0C it activatesCable break on the outdoor temperature sensorVitotronic 050/200-H
18, D1Fault in burnerThe DIP switch S2 is onVitodens 100-W
19Operation based on the outdoor temperature of 0CWireless outdoor temperature sensor

Fault with communication
Vitotronic 300
20Supply temperature may not be high enough

Vitocontrol-S controls in a stand alone manner without supply temperature sensor
Temperature sensor has shorted outVitocontrol-S with Vitotronic 100

Vitotronic 200, 300-K
20Low loss header

Temperature sensor regulates without supply
System supply temperature sensor has short circuitedVitodens 200-W, 222-F
20Supply 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 circuitedVitocontrol-S with Vitotronic 100

Vitotronic 100, 200, 300, 300-K
20Supply temperature may not be high enough

MW1S controls in a stand-alone manner without strap-on sensor
The strap-on temperature sensor has short circuitedVitotronic 100, 300-K
20Low loss header

Temperature sensor regulates without supply
System flow temperature sensor has short circuitedVitocrossal 300
20Mixing valve closedSupply temperature sensor has short circuited

Mixing valve circuit M1
Vitotronic 050/200-H, 200, 200-H, 300
20Low loss header

Temperature sensor regulates without supply
The system supply temperature sensor has shorted outVitodens 200-W
21Return water temperature operation without influenceReturn water temperature sensor short circuitedVitotronic 200, 300
25There 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 symbolVitodens 200
26Continuous relay test when the boiler is in operationFor 30 minutes the setting mode for minimum or maximum rated input has been activeVitodens 200
28Mixing valve is closedOpen circuit on the supply temperature sensor of the mixing valve circuit M1Vitotronic 050/200H
28Low loss header

Regulates without supply temperature sensor
Cable broken on the system supply temperature sensorVitocrossal 300

Vitodens 200-W, 222-F
28Mixing valve closesCable broken on the supply temperature sensorVitotronic 050/200H
28Stand-alone control unit without supply temperature sensor

The temperature may not be high enough
Common supply temperature sensor, lead breakVitotronic 300, 300-K
28Vitotronic 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 circuitVitotronic 100, 300-K
28Vitocontrol-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 sensorVitocontrol-S

Vitotronic 100, 300-K
28Vitocontrol-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 circuitVitotronic 100

Vitocontrol-S
28Mixing valve is in the process of being closedHeating circuit with mixing valve M1

Lead break

Supply temperature sensor
Vitotronic 200, 200-H, 300
29, 41, 49, F80, F81, F83, F88 and F89No influence of return water temperature and normal operationReturn water temperature sensor has an open circuit 1 or 2Vitotronic 200, 300
30The burner is started and stopped via adjustable high limitWater temperature sensor has short circuitedVitocontrol-S

Vitoronic 100, 200, 300

Vitodens 200-W, 222-F

Vitocrossal 300
30Blocked burnerThe water temperature sensor shorted outVitocontrol-S

Vitotronic 100

Vitodens 100-W (CombiPLUS), 200-1
35The boiler doesn't activateThe reset button has been pressed, whilst the burner is off, but the emissions test switch is turned to the hand symbolVitodens 200
38Blocked burnerWater temperature sensor lead brokenVitodens 100-W
38Temperature controller starts and stops the burnerWater temperature sensor

Lead break
Vitotronic 300-K, 300
38Blocked burnerCable broken on water temperature sensorVitodens 200-W, 222-F, CombiPLUS
38Burner switched on and off by the adjustable high limitTemperature sensor has an open circuitVitotronic 100, 200, 300

Vitocontrol-S
40, 44Mixing valve closesHeating circuit 2 with mixing valve supply short circuit on temperature sensorAll Viessmann boilers
48, 4CMixing valve is closing or has closedCable broken on mixing valve supply temperature sensor, it has an open circuit (Heating circuit 2)All Viessmann boilers
50, 51, 58, 59Fault with DHW

No DHW heating
DHW tank temperature sensor or lead break has short circuited or an open circuitVitodens 200-W, 222-F
52Control modeLow loss header with temperature sensor supply which has short circuitedVitotronic 300
52Blocked burnerShorted out flow sensorVitodens 100-W CombiPLUS
55, 56, 57Control modeMaintenance or errorVitotronic 300-K, 200
60, 68, 70, 78, BD, BE, BFNo output reduction

Open return control

Maximum temperature
Temperature sensor has short circuited or an open circuitAll Viessmann boilers
80, 81, 82, 83, FDFault state in burner control unit

System cools down

Burner control unit locked out
Water temperature sensor or burner control unit has short circuitedAll Viessmann boilers
88, 89, E6Fault state with the burner control unitBurner control unit

Water temperature sensor

Lead break
Vitotronic 300
90, 91, 92, 93, 94, 98, 99, 9A, 9B , 9C, 9E, 9F, ABControl modeTemperature sensor has short circuitedAll Viessmann boilers
A0, A1, A2, AA, ACThe boiler cools downFault with the safety equipment at X2, X3, X7 of plugin adaptor 2Vitotronic 300, 300-K
A0, A1, A2, AA, ACBUS fault: Boiler operates in emergency mode or the boiler cools downBUS fault or open circuit on internal BUS connectionVitodens 200
A2N/AFault with the KM-BUSVitodens 200
A3, B0, F1, FE1, FE2Blocked burnerCheck flue gas temperature centre, it may not be properly positionedAll Viessmann boilers
A4Maximum speed reached for pumpOpen circuit in BUS connection with variable speed heating circuit pumpVitodens 200
A5N/AShort or open circuitVitodens 200
A7Factory default control modeProgramming unit faultyVitocrossal 300

Vitodens 200-W, 222-F, 300
A8Blocked burner, automatically started venting programMinimum flow rate has not been achieved or air lock in internal circulation pumpVitodens 222-F
A9, BA, BB, BC, FE0Control modeCommunication errorAll Viessmann boilers
ADControl modeConfiguration error with isolation valve (OC:2, OC:3, OC:4 set), (4E:1 not set)Vitocontrol-S

Vitotronic 100, 300, 300-K
B1Control modeCommunication error with programming unitAll Viessmann boilers
B2Boiler cools downSensor inputs are not being read correctlyVitodens 200
B3, E5Not possible to set via service levelInternal fault, data points not stored (VR20)Vitodens 200
B4Control characteristics undefinedFault with internal electronicsVitotronic 050/200-H
B4Regulates as if outside temperature was at 0CFault interallyVitocontrol-S

Vitotronic 100

Vitodens 200-W
B4Emissions test modeFault with internal electronicsVitocontrol-S

Vitotronic 100, 200, 300, 300-K
B5Control modeFault with internal electronicsAll Viessmann boilers
B6Constant modeRecognisation of invalid hardwareAll Viessmann boilers
B9, ED, F0, FE5, FEC, FED, FEE, FEF, FFD, FFFFault of boiler control unit

Normal operation
Fault interallyAll Viessmann boilers
C1Control modeExternal safety equipmentAll Viessmann boilers
C2-C8, CD-CF, D2-D8, DA-DF, E0Control modeOpen circuit on KM BUS to solar control unit

AM1 Extension

DE-DE3 M1

Communication fault
All Viessmann boilers
C9, CA, CBBoiler cools downMaximum pressure limited errorVitocontrol-S

Vitotronic 100, 300, 300-K
CC, F0Large voltage fluctuations means the burner control unit switches to lockoutDifferential air pressure sensor or open circuitVitodens 200
D4Boiler cools downFuse F2 has blown or fixed high limit has respondedAll Viessmann boilers
D5Boiler drives up to electronic maximum limitThe boiler is not logging in at the cascade control unitAll Viessmann boilers
E1, E7, E8, E9, EA, EB, EC, FF2Fault mode in relation to burnerDuring calibration ionization is too highAll Viessmann boilers
E2, E3Fault mode in relation to burnerWater flow rate too low during calibration

Flow switch has caused shutdown
Vitodens 200-W, 222-F

Vitotronic 300
E4Blocked burnerVoltage supply faulty (24V)All Viessmann boilers
EE, EFFault mode in relation to burnerWhen the burner starts the flame signal is too weak or missingVitocontrol-S

Vitotronic 100, 300

Vitodens 200-W, 222-F

Vitocrossal 300
F5Blocked burnerAir pressure switch faultyVitodens 100-W, 200, 300

Vitotronic 300
F6, 58, F9, FE1, FE2, FF6Gas 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
All Viessmann boilers
FA, FBFault mode in relation to burner

Emergency operation
Plug-in connection

Fan not at standstill
All Viessmann boilers
FB7, FF4, FF2, FF7, FF8, FF9Fault 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
Vitocrossal 200
FCFault mode in relation to burnerFaulty gas valve

Faulty modulation valve control

Vent system blocked
All Viessmann boilers
FEFault mode in relation to burnerFaulty main printed circuit board

Strong interference field nearby
All Viessmann boilers
FE4Burner has shut downUnder set voltage detected multiple timesVitocrossal 200
FFA, FFB, FRFault mode in relation to burner

Fan runs without demand
Fan has not stopped

Faulty 100A cable

Faulty fan

Fault with burner control unit
Vitocrossal 200, 400-620, 186-311