BoilerFaultCodes 00:2
This code is not actually an error; it is simply a display message confirming your boiler is correctly set up to manage your standard heating and hot water.
Viessmann Vitodens 333 Fault codes & diagnostics
75 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Combi Natural GasLPG 26-35 kW 2004-2011 Discontinued
GC Number 47-819-15
Replaced by: Vitodens 222-F
The fault code is already on your display
Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →
Severity at a glance
Each cell = one fault code. Hover to identify. 1 Emergency
33 High
18 Medium
23 Low
Just want the most common Viessmann Vitodens 333 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 75 documented codes
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00:4 Your boiler's internal settings are currently configured to manage your home heating zones and hot water separately, which is a normal state for this model rather than a sign of a mechanical failure.
Your boiler's internal settings are currently configured to manage your home heating zones and hot water separately, which is a normal state for this model rather than a sign of a mechanical failure.
Related codes
00:6
This code indicates your boiler's system configuration settings have been detected, and it is functioning as intended based on your current home heating setup.
0F Your boiler is reminding you that its scheduled annual service is now due, but it should continue to provide heating and hot water as normal.
Your boiler is reminding you that its scheduled annual service is now due, but it should continue to provide heating and hot water as normal.
Parts commonly replaced
- Service kit (seals and electrodes)
- Burner gasket
Related codes
1E:0
Your boiler is operating normally using natural gas, and this code is simply providing status information rather than signalling a problem.
1E:1 Your boiler has detected that it is running on LPG gas rather than standard mains gas, which prevents it from operating safely.
Your boiler has detected that it is running on LPG gas rather than standard mains gas, which prevents it from operating safely.
Parts commonly replaced
- Coding Card
- Control Unit
2F:0 Your boiler is currently stuck in an automated air-clearing or water-filling mode, meaning it cannot provide heat or hot water until the cycle is finished or reset.
Your boiler is currently stuck in an automated air-clearing or water-filling mode, meaning it cannot provide heat or hot water until the cycle is finished or reset.
Parts commonly replaced
- Control unit
- Water pressure sensor
Related codes
2F:1
Your boiler is currently performing a necessary internal air-clearing process and will resume normal operation automatically once it is finished.
2F:2 Your boiler is currently running a maintenance program intended to purge air from the system after it was recently filled with water.
Your boiler is currently running a maintenance program intended to purge air from the system after it was recently filled with water.
What to check first
- Wait for the filling program to complete automatically, which usually takes about 20 minutes.
- Ensure your heating controls are set to a demand state if the boiler does not exit the mode on its own.
- If the code persists after 30 minutes, switch the boiler off at the fused spur for one minute and turn it back on to reset.
Related codes
06:... Your boiler has detected that it is getting too hot and has automatically switched itself off to prevent potential damage.
Your boiler has detected that it is getting too hot and has automatically switched itself off to prevent potential damage.
Parts commonly replaced
- Temperature sensor
- Circulation pump
- Diverter valve
- Heat exchanger
Showing 11–20 of 75
9A Your boiler has lost communication with the sensor that monitors your solar heating panels, likely due to a damaged or disconnected wire.
Your boiler has lost communication with the sensor that monitors your solar heating panels, likely due to a damaged or disconnected wire.
Parts commonly replaced
- Solar collector temperature sensor
- NTC thermistor wiring harness
Related codes
9B Your boiler has lost connection with its internal hot water storage sensor and cannot currently heat your water effectively or safely.
Your boiler has lost connection with its internal hot water storage sensor and cannot currently heat your water effectively or safely.
Parts commonly replaced
- Hot water cylinder temperature sensor (NTC)
- Sensor wiring harness
Related codes
9C Your boiler has lost connection with the sensor that monitors the temperature of your hot water cylinder, meaning it cannot heat your water correctly.
Your boiler has lost connection with the sensor that monitors the temperature of your hot water cylinder, meaning it cannot heat your water correctly.
Parts commonly replaced
- NTC Cylinder Temperature Sensor
- Sensor Wiring Harness
9F Your boiler is struggling to communicate with the solar panel system used to help heat your water.
Your boiler is struggling to communicate with the solar panel system used to help heat your water.
Parts commonly replaced
- Solar control module
- Communication cable
- Solar pump station PCB
Related codes
10 Your boiler's outside thermometer has developed a fault, causing the system to 'think' it is 0°C outside and adjust your heating accordingly.
Your boiler's outside thermometer has developed a fault, causing the system to 'think' it is 0°C outside and adjust your heating accordingly.
Parts commonly replaced
- Outside temperature sensor
- NTC thermistor
- Wiring harness
Related codes
18 Your boiler is confused about the weather outside because the external sensor has lost its connection, meaning the heating might not adjust correctly to the outdoor temperature.
Your boiler is confused about the weather outside because the external sensor has lost its connection, meaning the heating might not adjust correctly to the outdoor temperature.
Parts commonly replaced
- Outside temperature sensor
- Sensor wiring/cabling
Related codes
20 Your boiler's internal computer has detected a faulty or damaged temperature sensor, preventing the system from accurately measuring how hot the water is.
Your boiler's internal computer has detected a faulty or damaged temperature sensor, preventing the system from accurately measuring how hot the water is.
Parts commonly replaced
- System flow temperature sensor (NTC)
- Wiring harness connector
Related codes
21:1 to 21:100 Your boiler is reminding you that it is due for its routine annual safety service based on the number of hours it has been running.
Your boiler is reminding you that it is due for its routine annual safety service based on the number of hours it has been running.
Parts commonly replaced
- None - this is a maintenance prompt
23:1 to 23:24 Your boiler is simply reminding you that the annual service interval you set has now been reached.
Your boiler is simply reminding you that the annual service interval you set has now been reached.
24:1 Your boiler is simply reminding you that it is time for its regular annual service to ensure it continues to run safely and efficiently.
Your boiler is simply reminding you that it is time for its regular annual service to ensure it continues to run safely and efficiently.
Showing 21–30 of 75
25:1 Your boiler is struggling to read the temperature outside, which means it cannot automatically adjust your heating to match the weather conditions.
Your boiler is struggling to read the temperature outside, which means it cannot automatically adjust your heating to match the weather conditions.
Parts commonly replaced
- Outside temperature sensor
- Wiring harness
28 Your boiler has lost communication with a sensor that monitors the temperature of the water flowing into your heating system, usually because of a loose or damaged wire.
Your boiler has lost communication with a sensor that monitors the temperature of the water flowing into your heating system, usually because of a loose or damaged wire.
Parts commonly replaced
- Flow temperature sensor (NTC)
- Wiring harness / Lead
Related codes
30 Your boiler has stopped working because its internal temperature sensor has developed an electrical fault and can no longer safely monitor the heat level.
Your boiler has stopped working because its internal temperature sensor has developed an electrical fault and can no longer safely monitor the heat level.
Parts commonly replaced
- Boiler temperature sensor (NTC thermistor)
- Sensor wiring harness
Related codes
38 Your boiler has stopped working because it cannot accurately measure its own internal temperature due to a broken or disconnected sensor wire.
Your boiler has stopped working because it cannot accurately measure its own internal temperature due to a broken or disconnected sensor wire.
Parts commonly replaced
- Boiler temperature sensor (NTC thermistor)
- Wiring harness / connecting cable
Related codes
40 Your boiler has detected a faulty temperature sensor in one of your heating zones, which is preventing that specific circuit from getting warm.
Your boiler has detected a faulty temperature sensor in one of your heating zones, which is preventing that specific circuit from getting warm.
Parts commonly replaced
- NTC Flow Temperature Sensor
- Wiring harness
Related codes
48 Your boiler has lost communication with the temperature sensor that controls your second heating circuit, causing that specific zone to stop heating correctly.
Your boiler has lost communication with the temperature sensor that controls your second heating circuit, causing that specific zone to stop heating correctly.
Parts commonly replaced
- Flow temperature sensor (NTC)
- Sensor wiring harness
Related codes
50 Your boiler is unable to heat your hot water because one of the internal temperature sensors has developed an electrical fault.
Your boiler is unable to heat your hot water because one of the internal temperature sensors has developed an electrical fault.
Parts commonly replaced
- Cylinder temperature sensor
- NTC sensor lead
- Sensor wiring harness
Related codes
51 Your boiler is unable to provide hot water because of a faulty internal sensor that has stopped communicating correctly.
Your boiler is unable to provide hot water because of a faulty internal sensor that has stopped communicating correctly.
Parts commonly replaced
- Domestic Hot Water Cylinder Temperature Sensor
- Sensor Wiring Harness
Related codes
58 Your boiler is unable to heat your hot water because a sensor responsible for monitoring the cylinder temperature has lost its connection or stopped working.
Your boiler is unable to heat your hot water because a sensor responsible for monitoring the cylinder temperature has lost its connection or stopped working.
Parts commonly replaced
- NTC Cylinder Temperature Sensor
- Sensor Wiring Harness
- Loading Sensor
Related codes
59 Your boiler is unable to heat your hot water because a sensor that monitors the temperature of the water cylinder has stopped communicating with the system.
Your boiler is unable to heat your hot water because a sensor that monitors the temperature of the water cylinder has stopped communicating with the system.
Parts commonly replaced
- NTC Cylinder Temperature Sensor
- Sensor wiring harness
Related codes
Showing 31–40 of 75
77:1 Your boiler is struggling to communicate with its internal control system, which usually means the settings for how different parts of your heating system talk to each other have been lost or scrambled.
Your boiler is struggling to communicate with its internal control system, which usually means the settings for how different parts of your heating system talk to each other have been lost or scrambled.
Parts commonly replaced
- Communication Module
- Main Control Board
92 Your boiler’s solar heating panel sensor has a wiring fault, meaning the system cannot correctly read the temperature of the water heated by the sun.
Your boiler’s solar heating panel sensor has a wiring fault, meaning the system cannot correctly read the temperature of the water heated by the sun.
Parts commonly replaced
- Solar collector temperature sensor (NTC)
- Sensor lead/cable
Related codes
93 Your boiler’s solar heating connection has a faulty sensor that is incorrectly detecting a short circuit, preventing your solar panels from helping to heat your water.
Your boiler’s solar heating connection has a faulty sensor that is incorrectly detecting a short circuit, preventing your solar panels from helping to heat your water.
Parts commonly replaced
- Solar temperature sensor (NTC)
- Sensor lead/connection cable
Related codes
94 Your boiler has detected a problem with the sensor that measures the water temperature in your solar cylinder, which may affect how your hot water is heated.
Your boiler has detected a problem with the sensor that measures the water temperature in your solar cylinder, which may affect how your hot water is heated.
Parts commonly replaced
- Cylinder temperature sensor (NTC)
- Wiring harness
Related codes
A5:5
Your boiler is currently saving energy by temporarily turning off the central heating pump because the weather outside is warm enough that your home does not need extra heat.
A7 Your boiler's control panel and the main internal computer are having trouble talking to each other, meaning the display might not work correctly or respond to your settings.
Your boiler's control panel and the main internal computer are having trouble talking to each other, meaning the display might not work correctly or respond to your settings.
Parts commonly replaced
- HMI Control Unit
- Communication Cable
- Electronic PCB
Related codes
b0 Your boiler has stopped working because it has detected a technical fault with the sensor that monitors the heat of the exhaust gases.
Your boiler has stopped working because it has detected a technical fault with the sensor that monitors the heat of the exhaust gases.
Parts commonly replaced
- Flue gas temperature sensor
- Wiring harness
Related codes
b1 Your boiler's main control panel is having trouble talking to the internal computer, meaning you cannot adjust settings or operate the unit effectively.
Your boiler's main control panel is having trouble talking to the internal computer, meaning you cannot adjust settings or operate the unit effectively.
Parts commonly replaced
- Programming Unit
- HMU (Heat Management Unit)
- Internal Communication Cable
Related codes
b4 Your boiler's internal computer is having trouble processing electrical signals correctly, which is preventing it from running its safety and efficiency tests.
Your boiler's internal computer is having trouble processing electrical signals correctly, which is preventing it from running its safety and efficiency tests.
Parts commonly replaced
- Main PCB (Control Board)
- Electronic Controller Interface
Related codes
b5 Your boiler's main internal computer has encountered a communication error and cannot control the heating process correctly.
Your boiler's main internal computer has encountered a communication error and cannot control the heating process correctly.
Parts commonly replaced
- Electronic Control Box (PCB)
- Internal coding plug
Related codes
Showing 41–50 of 75
b7 Your boiler has stopped working because it cannot communicate with its internal memory chip or the main control board is malfunctioning.
Your boiler has stopped working because it cannot communicate with its internal memory chip or the main control board is malfunctioning.
Parts commonly replaced
- Boiler coding card
- Main PCB (Printed Circuit Board)
Related codes
b8 Your boiler has shut down because it cannot accurately measure the temperature of the exhaust gases, causing the burner to stop for safety.
Your boiler has shut down because it cannot accurately measure the temperature of the exhaust gases, causing the burner to stop for safety.
Parts commonly replaced
- Flue gas temperature sensor
- Wiring harness connector
Related codes
bA Your boiler is having trouble communicating with the control kit that manages the heating for your secondary radiator or underfloor heating zone.
Your boiler is having trouble communicating with the control kit that manages the heating for your secondary radiator or underfloor heating zone.
Parts commonly replaced
- Mixer circuit extension kit
- KM-BUS communication cable
- Mixer motor
Related codes
bC Your boiler has lost its connection with the remote control unit used to manage the heating and is currently operating in a basic backup mode.
Your boiler has lost its connection with the remote control unit used to manage the heating and is currently operating in a basic backup mode.
What to check first
- Check that the Vitotrol remote control unit is correctly seated on its wall bracket.
- Inspect the remote control for any dead batteries if it is a wireless version.
- Perform a power reset on the boiler to see if communication re-establishes.
Parts commonly replaced
- Vitotrol remote control
- Communication cable
- Internal KM-BUS module
Related codes
bd Your boiler has lost communication with your remote room thermostat or heating controller for the second heating circuit.
Your boiler has lost communication with your remote room thermostat or heating controller for the second heating circuit.
What to check first
- Check if the batteries in your wall-mounted thermostat need replacing
- Ensure the thermostat is within signal range of the boiler
- Turn the boiler off and back on at the fused spur switch to reset the connection
Parts commonly replaced
- Vitotrol Remote Control unit
- Communication module
- Wiring harness
Related codes
bE Your wall-mounted remote control unit is not communicating correctly with the boiler because of a settings error.
Your wall-mounted remote control unit is not communicating correctly with the boiler because of a settings error.
Parts commonly replaced
- Vitotrol Remote Control unit
- Communication module
Related codes
bF Your boiler's internal communication system has detected an issue with a plug-in connection module, meaning the main control board cannot talk to other system components properly.
Your boiler's internal communication system has detected an issue with a plug-in connection module, meaning the main control board cannot talk to other system components properly.
Parts commonly replaced
- LON communication module
- Electronic control PCB
Related codes
C2 Your boiler is having trouble talking to the solar heating system, which may prevent your home from using energy from your solar panels efficiently.
Your boiler is having trouble talking to the solar heating system, which may prevent your home from using energy from your solar panels efficiently.
What to check first
- Check that the solar control unit is switched on and has power
- Turn the boiler power off at the fused spur, wait 30 seconds, and turn it back on to reset the connection
- Inspect any visible cables between the boiler and the solar controller for obvious signs of damage or loose plugs
Parts commonly replaced
- Communication cable
- Solar control module (Vitosolic)
- Electronic controller
C5 Your boiler is having trouble communicating with its internal pump, which means water cannot circulate properly to heat your home.
Your boiler is having trouble communicating with its internal pump, which means water cannot circulate properly to heat your home.
Parts commonly replaced
- Internal circulation pump
- Wiring harness
- Main PCB
Related codes
C5:20 Your boiler has detected that the water temperature is currently below the required minimum safety level, causing it to pause heating to prevent potential condensation issues.
Your boiler has detected that the water temperature is currently below the required minimum safety level, causing it to pause heating to prevent potential condensation issues.
Parts commonly replaced
- NTC Temperature sensor
- Circulation pump
- Main PCB
Showing 51–60 of 75
C6 Your boiler is having trouble communicating with the internal pump that manages one of your heating circuits, meaning that part of your heating may not be working correctly.
Your boiler is having trouble communicating with the internal pump that manages one of your heating circuits, meaning that part of your heating may not be working correctly.
Parts commonly replaced
- Circulation pump
- Pump wiring harness
- Main PCB
Related codes
C6:75 Your boiler has detected that the water inside is getting too hot and has temporarily restricted itself to prevent overheating and ensure safe operation.
Your boiler has detected that the water inside is getting too hot and has temporarily restricted itself to prevent overheating and ensure safe operation.
Parts commonly replaced
- NTC Temperature Sensor
- Flow Pipe Thermostat
- Main Printed Circuit Board
C7 Your boiler is having trouble communicating with the internal pump that moves water around your radiators, which may lead to your heating not working effectively.
Your boiler is having trouble communicating with the internal pump that moves water around your radiators, which may lead to your heating not working effectively.
Parts commonly replaced
- Circulation Pump
- Internal Wiring Harness
- Electronic Control Board
Related codes
Cd Your boiler has lost its connection with the external remote control or internet communication module.
Your boiler has lost its connection with the external remote control or internet communication module.
What to check first
- Check that your internet router is switched on and functioning
- Ensure the Vitocom communication module is plugged in and powered
- Reset your boiler by turning it off and on again to re-establish the link
Parts commonly replaced
- Vitocom 100 Communication Module
- KM-BUS Connection Cable
Related codes
CE Your boiler is having trouble 'talking' to an add-on device, such as an extra heating controller or an external sensor module.
Your boiler is having trouble 'talking' to an add-on device, such as an extra heating controller or an external sensor module.
Parts commonly replaced
- External extension module
- Communication cable (Bus line)
- Electronic control board
Related codes
CF Your boiler's internal communication system has failed, meaning the different electronic parts are no longer talking to each other correctly.
Your boiler's internal communication system has failed, meaning the different electronic parts are no longer talking to each other correctly.
Parts commonly replaced
- LON communication module
- Boiler control board (PCB)
- LON connecting cable
Related codes
d3:14
This code is not a fault; it is simply a display setting confirming your boiler's current programming for how much it increases water temperature based on the outdoor weather.
d4:0 Your boiler is telling you that the heating system settings are currently turned down to zero, which means it will not provide any heat to your radiators.
Your boiler is telling you that the heating system settings are currently turned down to zero, which means it will not provide any heat to your radiators.
What to check first
- Locate the main display panel on your boiler.
- Access the 'Heating' or 'Comfort' menu settings.
- Adjust the heating curve or target room temperature to a value above zero.
dA Your boiler has lost its connection to the indoor thermostat sensor, meaning it can no longer adjust the heating based on the actual temperature inside your home.
Your boiler has lost its connection to the indoor thermostat sensor, meaning it can no longer adjust the heating based on the actual temperature inside your home.
Parts commonly replaced
- NTC Room Temperature Sensor
- Sensor Wiring harness
Related codes
db Your boiler has lost its connection to one of the temperature sensors used to control your heating, though it will likely keep running in a basic backup mode.
Your boiler has lost its connection to one of the temperature sensors used to control your heating, though it will likely keep running in a basic backup mode.
Parts commonly replaced
- Room temperature sensor (NTC)
- Sensor wiring harness
Related codes
Showing 61–70 of 75
dE Your boiler has lost connection to one of its internal temperature sensors, which means it cannot accurately monitor the heat for one of your heating zones.
Your boiler has lost connection to one of its internal temperature sensors, which means it cannot accurately monitor the heat for one of your heating zones.
Parts commonly replaced
- NTC Temperature Sensor
- Sensor Wiring Harness
- Control Unit Connection Plug
E4 Your boiler has stopped working because it is not receiving the correct electrical supply, preventing the burner from igniting.
Your boiler has stopped working because it is not receiving the correct electrical supply, preventing the burner from igniting.
Parts commonly replaced
- Ignition Transformer
- Electronic Control Board
- Wiring Harness
Related codes
E5 Your boiler has stopped working because it cannot properly detect the flame it needs to stay lit safely.
Your boiler has stopped working because it cannot properly detect the flame it needs to stay lit safely.
Parts commonly replaced
- Ionisation electrode
- Ignition lead
- Burner control unit
- Flue seals
Related codes
E6 Your boiler has shut down because it cannot safely vent exhaust gases or draw in fresh air, usually due to a blockage in the flue pipe or a hardware failure.
Your boiler has shut down because it cannot safely vent exhaust gases or draw in fresh air, usually due to a blockage in the flue pipe or a hardware failure.
Parts commonly replaced
- Flue Gas Pressure Switch
- Fan Assembly
- Burner Gasket
Related codes
F0 Your boiler has stopped working because its internal computer and burner system have detected a technical communication failure.
Your boiler has stopped working because its internal computer and burner system have detected a technical communication failure.
Parts commonly replaced
- Electronic Control Unit (PCB)
- Communication Cable
Related codes
F1 Your boiler has shut down because it detected that the exhaust gases have become too hot, which is a safety feature to prevent damage or dangerous operation.
Your boiler has shut down because it detected that the exhaust gases have become too hot, which is a safety feature to prevent damage or dangerous operation.
Parts commonly replaced
- Flue gas temperature sensor
- Heat exchanger (cleaning/descaling)
- Burner gasket
Related codes
F2 Your boiler has shut down because it has overheated or detected a lack of water flow through the system.
Your boiler has shut down because it has overheated or detected a lack of water flow through the system.
What to check first
- Check the pressure gauge and top up water if it is below 1.5 bar
- Bleed your radiators to remove trapped air
- Press the 'Reset' or 'E' button to restart the boiler
Parts commonly replaced
- Circulation pump
- High limit thermostat
- Heat exchanger (flushing/cleaning)
Related codes
F3 Your boiler has shut down because it thinks it can see a flame before it has even started the ignition process.
Your boiler has shut down because it thinks it can see a flame before it has even started the ignition process.
Parts commonly replaced
- Ionisation electrode
- Ignition lead
- Burner control unit (PCB)
Related codes
F4 Your boiler is failing to light the flame needed to heat your water and radiators, which has caused the system to shut down for safety.
Your boiler is failing to light the flame needed to heat your water and radiators, which has caused the system to shut down for safety.
Parts commonly replaced
- Ionisation electrode
- Ignition leads
- Gas combination valve
- Ignition unit
Related codes
F7 Your boiler has shut down because it is unable to accurately measure the air pressure required for its burner to operate safely.
Your boiler has shut down because it is unable to accurately measure the air pressure required for its burner to operate safely.
Parts commonly replaced
- Differential pressure sensor
- Wiring harness
- Fan assembly
Related codes
Showing 71–75 of 75
F8 Your boiler has detected a potential issue with the valve that controls the gas supply, meaning it isn't shutting off correctly for safety.
Your boiler has detected a potential issue with the valve that controls the gas supply, meaning it isn't shutting off correctly for safety.
Parts commonly replaced
- Gas combination valve
- Electronic control unit
- Ignition electrodes
Related codes
F9 Your boiler's fan is not spinning fast enough to safely start the burner, causing the system to shut down for safety.
Your boiler's fan is not spinning fast enough to safely start the burner, causing the system to shut down for safety.
Parts commonly replaced
- Fan assembly
- Fan wiring harness
- Burner control unit
Related codes
FA Your boiler has stopped working because the internal fan is spinning too fast during the startup process, preventing the burner from igniting safely.
Your boiler has stopped working because the internal fan is spinning too fast during the startup process, preventing the burner from igniting safely.
Parts commonly replaced
- Extraction Fan
- Fan Control Lead
- Burner Control Unit / PCB
Related codes
Fd Your boiler's internal computer has detected a problem with the burner's ignition system and has shut down as a safety precaution.
Your boiler's internal computer has detected a problem with the burner's ignition system and has shut down as a safety precaution.
Parts commonly replaced
- Ignition electrodes
- Ignition leads
- Control unit (PCB)
Related codes
FE Your boiler has shut down because electronic interference or a faulty internal circuit board is preventing the burner from starting safely.
Your boiler has shut down because electronic interference or a faulty internal circuit board is preventing the burner from starting safely.
What to check first
- Turn off any nearby large electrical appliances or power tools that might cause electronic interference.
- Press the reset button or turn the boiler off and back on at the fused spur.
- If the fault persists after a reset, you must call a Gas Safe registered engineer.
Parts commonly replaced
- Boiler coding card
- Main PCB (Control Unit)