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Viessmann Vitodens 200-W and 300-W fault codes

Fault codes are displayed when the (heating) program has to be aborted due to a fault message. They indicate causes of faults as well as possible measures that should only be carried out by an authorised contractor.

As the owner of the system, however, you will receive a rough guide with the respective fault code and a corresponding brief description, so that you can better describe the situation to your contractor. To find a suitable trade partner in your area, simply use our trade partner search.

Fault codes should be analysed by a contractor

The following Viessmann fault codes refer to the 200 and 300 series of wall mounted gas boilers with Vitotronic control unit, including the Vitodens 200-W and Vitodens 300-W, as well as the Vitodens 222-W, the Vitodens 222-F and the Vitodens 333-F. Fault codes for newer models may differ. As mentioned at the beginning, fault codes and their possible measures only serve as a rough guide for system users. We strongly advise against carrying out the measures by yourself. After all,

  • incorrectly executed work on the heating system can lead to life threatening accidents. 
  • If this is disregarded, the statutory warranty may become invalid.
  • All adjustments and work on the appliance must be performed as specified in the respective operating instructions.
  • Further work on the appliance may be carried out only by authorised contractors.

For information on how to make adjustments on your boiler and what you should pay attention to, please refer to the Viessmann operating instructions for your boiler. You can find these in our ViBooks database, for example.

As a general rule:

  • Do not open the appliance
  • Do not remove casings
  • Do not modify or remove attachments or fitted accessories
  • Do not open or tighten pipe connections

Viessmann fault codes do not apply to all heating systems

Note: the fault codes listed here apply exclusively to the gas condensing models of the 200 and 300 series with Vitotronic control unit. Solid fuel boilers, heat pumps, CHP units and other systems have their own fault codes. Furthermore, the following list does not claim to be complete and is intended only as a guide.

Look up fault codes online

You can also use our online database to look up the behaviour of the system and the cause of the fault for a displayed fault code. In addition to the fault code, you will need the part/serial number of your Viessmann product. You can find this on the control unit/product type plate.

Please contact your contractor if you have any questions and to remedy the cause of the fault. If your heating system is already connected to the ViCare app, you can simply forward the fault message to your contractor with one click. 

Fault codes for 200 and 300 series wall mounted gas boilers with Vitotronic control unit


Note: some measures include coding addresses or coding groups. The setting of these codes may only be carried out by authorised contractors.

Displayed fault code System characteristics Cause of fault Measure
10 Regulates as if the outside temperature were 0 °C Short circuit, outside temperature sensor Check outside temperature sensor
18 Regulates as if the outside temperature were 0 °C Lead break, outside temperature sensor Check outside temperature sensor
19 Regulates as if the outside temperature were 0 °C Interruption of RF outside temperature sensor communication (RF outside temperature sensor, KM-BUS to wireless base station, wireless base station or wireless repeater faulty or defective) Check wireless connection (place RF outside temperature sensor and wireless repeater close to the boiler). Check KM-BUS to wireless base station. Log off outside temperature sensor and wireless repeater, then log them on again. Replace RF outside temperature sensor. Replace wireless repeater. Replace wireless base station
20 Regulates without flow temperature sensor (low loss header) Short circuit, system flow temperature sensor Check the low loss header sensor
28 Regulates without flow temperature sensor (low loss header) Lead break, system flow temperature sensor Check the low loss header sensor. If no low loss header sensor is connected, set code 52:0
30 Burner locked out Short circuit, boiler water temperature sensor Check boiler water temperature sensors
38 Burner locked out Lead break, boiler water temperature sensor Check boiler water temperature sensors
40 Mixer is being closed Short circuit, flow temperature sensor, heating circuit 2 (with mixer) Check flow temperature sensor
44 Mixer is being closed Short circuit, flow temperature sensor, heating circuit 3 (with mixer) Check flow temperature sensor
48 Mixer is being closed Short circuit, flow temperature sensor, heating circuit 2 (with mixer) Check flow temperature sensor
50 No DHW heating by the boiler Short circuit, cylinder temperature sensor Check cylinder temperature sensor
58 No DHW heating No DHW heating by the boiler Check cylinder temperature sensor
90 Normal operation Short circuit, temperature sensor Check sensor on the solar control module
91 Normal operation Short circuit, temperature sensor Check sensor on the solar control module
92 No solar DHW heating Short circuit, collector temperature sensor Check temperature sensor on the solar control module or the sensor on the Vitosolic
93 Normal operation Short circuit, collector return temperature sensor Check temperature sensor at connection S3 on the Vitosolic
94 No solar DHW heating Short circuit, cylinder temperature sensor Temperature sensor on the solar control module
98 Normal operation Lead break, temperature sensor Check sensor on the solar control module
99 Normal operation Lead break, temperature sensor Check sensor on the solar control module
1A Burner locked out Flow sensor 1, left (plug 163) faulty Replace the sensor
1b Burner locked out Flow sensor 2, right (plug 163A) faulty Replace the sensor
1F Burner locked out Differential flow rate too large Clean heat exchanger by flushing
4C Mixer is being closed Lead break, flow temperature sensor, heating circuit 3 (with mixer) Check flow temperature sensor
9A No solar DHW heating Lead break, collector temperature sensor Check temperature sensor on the solar control module or the sensor on the Vitosolic
9b Normal operation Lead break, collector return temperature sensor Check temperature sensor at connection S3 on the Vitosolic
9C No solar DHW heating Lead break, cylinder temperature sensor Check temperature sensor on the solar control module or the sensor on the Vitosolic
9E Normal operation No flow or flow rate too low in the solar circuit, or temperature limiter has responded Check solar circuit pump and solar circuit. Acknowledge fault message
9F Normal operation Solar control module or Vitosolic fault Replace solar control module or Vitosolic
A3 Burner locked out Flue gas temperature sensor incorrectly positioned Fit flue gas temperature sensor correctly
A4 Normal operation Max. system pressure exceeded Check system pressure (max. system pressure 6 bar). Check the function and sizing of the diaphragm pressure expansion vessel. Vent the heating system
A7 Normal operation as per delivered condition Programming unit faulty Replace the programming unit
b0 Burner locked out Short circuit, flue gas temperature sensor Check flue gas temperature sensor
b1 Normal operation as per delivered condition Communication error, programming unit Check connections and replace programming unit if necessary
b5 Normal operation as per delivered condition Internal fault Replace control unit
b7 Burner locked out Fault, boiler coding card Plug in boiler coding card or replace if faulty
b8 Burner locked out Lead break, flue gas temperature sensor Check flue gas temperature sensor
bA Mixer regulates to 20 °C flow temperature Communication error, extension kit for heating circuit 2 (with mixer) Check extension kit connections and code
bb Mixer regulates to 20 °C flow temperature Communication error, extension kit for heating circuit 3 (with mixer) Check extension kit connections and code
bC Normal operation without remote control Communication error, Vitotrol remote control, heating circuit 1 (without mixer) Check connections, cable and coding address "A0" in the "Heating circuit" group and the DIP switch on the remote control unit. With wireless remote controls: check transmission path connections; place remote control and wireless repeater close to the boiler. Check KM-BUS connection to wireless base station. Replace the wireless components
bd Normal operation without remote control Communication error, Vitotrol remote control, heating circuit 2 (with mixer) Check connections, cable and coding address "A0" in the "Heating circuit" group and the remote control settings. With wireless remote controls: check transmission path connections; place remote control and wireless repeater close to the boiler. Check KM-BUS connection to wireless base station. Replace the wireless components
bE Normal operation without remote control Communication error, Vitotrol remote control, heating circuit 3 (with mixer) Check connections, cable and coding address "A0" in the "Heating circuit" group and the remote control settings. With wireless remote controls: check transmission path connections; place remote control and wireless repeater close to the boiler. Check KM-BUS connection to wireless base station. Replace the wireless components
bF Normal operation Wrong LON communication module Replace LON communication module
C1 Normal operation Communication error, EA1 extension Check the connections
C2 Normal operation Communication error, solar control module or Vitosolic Check solar control module or Vitosolic
C3 Normal operation Communication error, AM1 extension Check the connections
C4 Normal operation Communication error, OpenTherm extension Check OpenTherm extension
C5 Normal operation, max. pump speed Communication error, variable speed pump Check pump KM-BUS
Cd Normal operation Communication error, Vitocom 100 (KM-BUS) Check connections, Vitocom 100 and coding address "95" in group "General"/1
CF Normal operation Communication error, LON communication module Replace LON communication module
d6 Normal operation DE1 input at EA1 extension reports a fault Remedy fault at affected appliance
d7 Normal operation DE2 input at EA1 extension reports a fault Remedy fault at affected appliance
d8 Normal operation DE3 input at EA1 extension reports a fault Remedy fault at affected appliance
dA Normal operation without room influence Short circuit, room temperature sensor, heating circuit 1 (without mixer) Check room temperature sensor, heating circuit 1
db Normal operation without room influence Short circuit, room temperature sensor, heating circuit 2 (with mixer) Check room temperature sensor, heating circuit 2
dC Normal operation without room influence Short circuit, room temperature sensor, heating circuit 3 (with mixer) Check room temperature sensor, heating circuit 3
dd Normal operation without room influence Lead break, room temperature sensor, heating circuit 1 (without mixer) Check room temperature sensor, heating circuit 1 and the remote control settings
dE Normal operation without room influence Lead break, room temperature sensor, heating circuit 2 (with mixer) Check room temperature sensor, heating circuit 2 and the remote control settings
dF Normal operation without room influence Lead break, room temperature sensor, heating circuit 3 (with mixer) Check room temperature sensor, heating circuit 3 and the remote control settings
E0 Normal operation External LON subscriber fault Check connections and LON subscribers
E3 Burner in a fault state Heat transfer too low during calibration. Temperature limiter has shut down Ensure adequate heat transfer. Press reset button R
E4 Burner locked out Fault, 24 V supply voltage Replace control unit
E5 Burner locked out Flame amplifier fault Replace control unit
Eb Burner in a fault state Repeated flame loss during calibration Check gap between ionisation electrode and burner gauze assembly. Check the allocation of the gas type. Check flue system; remove flue gas recirculation if necessary. Press reset button R
EC Burner in a fault state Parameter fault during calibration Press reset button R or replace the boiler coding card and then press reset button R
Ed Burner in a fault state Internal fault Replace control unit
F0 Burner locked out Internal fault Replace control unit
F1 Burner in a fault state Flue gas temperature has exceeded limit Check heating system fill level. Vent the system. Press reset button R after the flue system has cooled down
F2 Burner in a fault state Boiler water temperature sensor has responded Check heating system fill level. Check circulation pump. Vent the system. Check boiler water temperature sensor and connecting cables. Press reset button R
F6 Burner in a fault state Temperature values of the boiler water temperature sensors vary too widely from one another Replace the boiler water temperature sensors
F8 Burner in a fault state Fuel valve closes late Check gas solenoid valve. Check both control paths. Press reset button R
FF Burner blocked or in a fault state Internal fault or reset button R blocked Restart the appliance. Replace the control unit if the appliance will not restart
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