BoilerFaultCodes 00:1
Your boiler is currently operating on its basic factory configuration for a simple heating system and is not indicating a fault.
Viessmann Vitodens 222-W Fault codes & diagnostics
108 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Combi Natural GasLPG 19-35 kW 2007-present
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Severity at a glance
Each cell = one fault code. Hover to identify. 56 High
18 Medium
34 Low
Just want the most common Viessmann Vitodens 222-W faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 108 documented codes
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00:2
This code is simply an information display showing your boiler's current setup configuration, rather than an error or a heating problem.
00:3
Your boiler is correctly operating in a specific configuration that manages one heating zone without providing domestic hot water.
00:4
This code is not actually a fault, but a status indicator confirming your boiler is configured to control both your radiators and your hot water tank separately.
00:5
Your boiler is correctly configured for your specific heating setup and this code is simply informing you how your system is currently set up to operate.
00:6
Your boiler is correctly configured for your specific home heating setup, and this code is simply an information status indicating how your system is set up to manage your radiators and hot water.
0A Your boiler has detected an issue with the gas pressure or a component failure and has shut down as a safety precaution.
Your boiler has detected an issue with the gas pressure or a component failure and has shut down as a safety precaution.
Parts commonly replaced
- Gas pressure switch
- Ignition electrodes
- Gas valve
- Burner control unit
Related codes
0D Your boiler has detected an internal communication error and has shut itself down as a safety precaution.
Your boiler has detected an internal communication error and has shut itself down as a safety precaution.
Parts commonly replaced
- Burner Control Unit
- Ignition Lead
- Main PCB
Related codes
0F Your boiler is simply reminding you that it is due for its regular annual service and there is no actual fault with the system.
Your boiler is simply reminding you that it is due for its regular annual service and there is no actual fault with the system.
Parts commonly replaced
- Service kit (gaskets and electrodes)
Related codes
1A Your boiler has shut down because it is struggling to discharge exhaust fumes safely or is detecting a significant lack of air flow.
Your boiler has shut down because it is struggling to discharge exhaust fumes safely or is detecting a significant lack of air flow.
Parts commonly replaced
- Flue gas sensor
- Heat exchanger (cleaning)
- Ventilation fan
- Condensate trap
Related codes
Showing 11–20 of 108
1B Your boiler has shut down because it is struggling to discharge exhaust fumes safely or is detecting a significant lack of air flow.
Your boiler has shut down because it is struggling to discharge exhaust fumes safely or is detecting a significant lack of air flow.
Parts commonly replaced
- Flue gas sensor
- Heat exchanger (cleaning)
- Ventilation fan
- Condensate trap
Related codes
1E:0
Your boiler is currently set up to run on natural gas and is operating normally.
1E:1
Your boiler is correctly identifying that it is running on LPG rather than mains natural gas, confirming that the initial installation settings match your fuel supply.
1F Your boiler has stopped working because the burner isn't lighting correctly, likely due to a problem with the internal airflow or the ignition system.
Your boiler has stopped working because the burner isn't lighting correctly, likely due to a problem with the internal airflow or the ignition system.
Parts commonly replaced
- Ionisation electrode
- Ignition lead
- Gas valve
- Fan assembly
Related codes
02 Your boiler has shut itself down as a safety precaution because it has detected an overheating issue within the system.
Your boiler has shut itself down as a safety precaution because it has detected an overheating issue within the system.
Parts commonly replaced
- Circulation pump
- Overheat thermostat
- Heat exchanger (cleaning/flush)
Related codes
2E:0 Your boiler is struggling to communicate with an optional add-on controller or sensor that it thinks should be connected.
Your boiler is struggling to communicate with an optional add-on controller or sensor that it thinks should be connected.
Parts commonly replaced
- External extension module
- Communication cable
- PCB
2F:0 Your boiler is currently stuck in or has failed to complete its internal air-purging process, preventing it from firing up normally.
Your boiler is currently stuck in or has failed to complete its internal air-purging process, preventing it from firing up normally.
Parts commonly replaced
- Control board/PCB
- Wiring harness
Related codes
2F:1 Your boiler is currently running a brief automated cycle to clear air from the system, which is a normal process.
Your boiler is currently running a brief automated cycle to clear air from the system, which is a normal process.
Related codes
2F:2 Your boiler is currently running an automated process to clear air out of the system after it was recently refilled or serviced.
Your boiler is currently running an automated process to clear air out of the system after it was recently refilled or serviced.
What to check first
- Wait 20 minutes for the automated program to finish.
- If the code persists, restart the boiler using the power switch.
- Ensure your system pressure is set correctly between 1.0 and 1.5 bar.
Related codes
04 Your boiler has detected a sequence of ignition or flame detection errors and has shut itself down for safety.
Your boiler has detected a sequence of ignition or flame detection errors and has shut itself down for safety.
Parts commonly replaced
- Ignition Electrode
- Ionisation Electrode
- Gas Valve
- Electronic Control Unit (PCB)
Related codes
Showing 21–30 of 108
05 Your boiler has detected a sequence of ignition or flame detection errors and has shut itself down for safety.
Your boiler has detected a sequence of ignition or flame detection errors and has shut itself down for safety.
Parts commonly replaced
- Ignition Electrode
- Ionisation Electrode
- Gas Valve
- Electronic Control Unit (PCB)
Related codes
06 Your boiler has detected a sequence of ignition or flame detection errors and has shut itself down for safety.
Your boiler has detected a sequence of ignition or flame detection errors and has shut itself down for safety.
Parts commonly replaced
- Ignition Electrode
- Ionisation Electrode
- Gas Valve
- Electronic Control Unit (PCB)
Related codes
06:... Your boiler has detected that the water inside the system has become dangerously hot and has shut itself down to prevent damage.
Your boiler has detected that the water inside the system has become dangerously hot and has shut itself down to prevent damage.
Parts commonly replaced
- Temperature sensor (NTC)
- Pump
- PCB
- Heat exchanger
Related codes
07 Your boiler has detected a sequence error or a flame signal where there shouldn't be one, causing the burner to shut down completely for safety.
Your boiler has detected a sequence error or a flame signal where there shouldn't be one, causing the burner to shut down completely for safety.
Parts commonly replaced
- Ionisation electrode
- Ignition cable
- Burner control unit (PCB)
Related codes
08 Your boiler has detected a sequence of ignition or flame detection errors and has shut itself down for safety.
Your boiler has detected a sequence of ignition or flame detection errors and has shut itself down for safety.
Parts commonly replaced
- Ignition Electrode
- Ionisation Electrode
- Gas Valve
- Electronic Control Unit (PCB)
Related codes
09 Your boiler has detected a sequence error or a flame signal where there shouldn't be one, causing the burner to shut down completely for safety.
Your boiler has detected a sequence error or a flame signal where there shouldn't be one, causing the burner to shut down completely for safety.
Parts commonly replaced
- Ionisation electrode
- Ignition cable
- Burner control unit (PCB)
Related codes
9A Your boiler has lost communication with the temperature sensor that monitors the outdoor solar panels or the system collector, meaning it cannot accurately manage heat levels for those components.
Your boiler has lost communication with the temperature sensor that monitors the outdoor solar panels or the system collector, meaning it cannot accurately manage heat levels for those components.
Parts commonly replaced
- Collector temperature sensor (NTC)
- Sensor wiring harness
Related codes
9B Your boiler has lost communication with one of its internal heat sensors, meaning it cannot monitor temperatures accurately to operate safely.
Your boiler has lost communication with one of its internal heat sensors, meaning it cannot monitor temperatures accurately to operate safely.
Parts commonly replaced
- Low loss header sensor
- NTC thermistor
- Wiring harness
Related codes
9C Your boiler is unable to read the temperature of your hot water cylinder because the connection to the sensor has been lost or damaged.
Your boiler is unable to read the temperature of your hot water cylinder because the connection to the sensor has been lost or damaged.
Parts commonly replaced
- NTC Cylinder Temperature Sensor
- Sensor wiring harness
Related codes
9F Your boiler has lost communication with the solar heating control panel, meaning your solar panels won't be helping to heat your water.
Your boiler has lost communication with the solar heating control panel, meaning your solar panels won't be helping to heat your water.
What to check first
- Check if the solar control panel has power
- Switch the boiler off and back on at the fused spur switch to reset the connection
- Check for any loose external cables connecting the solar controller to the boiler if visible and safe
Parts commonly replaced
- Solar control module
- Communication cable
- Solar cylinder temperature sensor
Related codes
Showing 31–40 of 108
10 Your boiler is struggling to accurately gauge the weather outside, meaning it might not provide the right amount of heat for your home.
Your boiler is struggling to accurately gauge the weather outside, meaning it might not provide the right amount of heat for your home.
Parts commonly replaced
- Outside temperature sensor
- NTC thermistor
- Wiring lead
Related codes
18 Your boiler has lost its connection to the outside temperature sensor, meaning it cannot automatically adjust your heating based on the weather.
Your boiler has lost its connection to the outside temperature sensor, meaning it cannot automatically adjust your heating based on the weather.
Parts commonly replaced
- Outside temperature sensor
- Sensor wiring
Related codes
20 Your boiler has detected an electrical fault with a sensor that monitors the water temperature flowing into your heating system, leading it to shut down for safety.
Your boiler has detected an electrical fault with a sensor that monitors the water temperature flowing into your heating system, leading it to shut down for safety.
Parts commonly replaced
- Flow temperature sensor (NTC)
- Sensor wiring harness
Related codes
21:0 Your boiler is simply notifying you that a routine service is due based on its operating hours.
Your boiler is simply notifying you that a routine service is due based on its operating hours.
23:0 Your boiler is simply reminding you that it is time for its regular annual service to ensure it continues running safely and efficiently.
Your boiler is simply reminding you that it is time for its regular annual service to ensure it continues running safely and efficiently.
24:0
Your boiler is simply indicating that no urgent service or maintenance is currently required at this time.
25 Your boiler is getting too hot too quickly and is shutting itself down to prevent damage.
Your boiler is getting too hot too quickly and is shutting itself down to prevent damage.
What to check first
- Check that your radiator valves are fully open
- Ensure the central heating pump is running
- Check if the system water pressure is between 1.0 and 1.5 bar
Parts commonly replaced
- Circulation pump
- Temperature sensors (NTC thermistors)
- Heat exchanger (descaling)
Related codes
25:0 Your boiler has lost the connection to the external sensor that tells it how cold it is outside, meaning it may not adjust its heating output as efficiently as usual.
Your boiler has lost the connection to the external sensor that tells it how cold it is outside, meaning it may not adjust its heating output as efficiently as usual.
Parts commonly replaced
- Outside temperature sensor
- Wiring harness
- Control PCB
25:1 Your boiler has lost the connection to the thermometer placed outside your home, so it cannot automatically adjust your heating based on the weather.
Your boiler has lost the connection to the thermometer placed outside your home, so it cannot automatically adjust your heating based on the weather.
Parts commonly replaced
- Outside temperature sensor
- Wiring loom/connection cable
Related codes
26 Your boiler's computer has become stuck in a repeating internal test sequence and is failing to move into its normal heating mode.
Your boiler's computer has become stuck in a repeating internal test sequence and is failing to move into its normal heating mode.
Parts commonly replaced
- Main VBC PCB (Control Board)
- Relay Module
Related codes
Showing 41–50 of 108
28 Your boiler has lost connection with a temperature sensor that monitors the main water flow, likely due to a broken wire or a faulty sensor.
Your boiler has lost connection with a temperature sensor that monitors the main water flow, likely due to a broken wire or a faulty sensor.
Parts commonly replaced
- Low loss header temperature sensor
- NTC thermistor
- Wiring harness
Related codes
28:0 Your boiler is failing to light the flame needed to produce heat or hot water.
Your boiler is failing to light the flame needed to produce heat or hot water.
Parts commonly replaced
- Ignition electrode
- Ignition transformer
- Gas valve
Related codes
30 Your boiler has stopped heating because a internal sensor that monitors water temperature has developed an electrical fault and is preventing the burner from firing.
Your boiler has stopped heating because a internal sensor that monitors water temperature has developed an electrical fault and is preventing the burner from firing.
Parts commonly replaced
- Boiler water temperature sensor (NTC thermistor)
- Wiring harness
Related codes
30:0 Your boiler has detected an issue with the water pump that moves heat around your radiators and taps, meaning it cannot circulate heat effectively.
Your boiler has detected an issue with the water pump that moves heat around your radiators and taps, meaning it cannot circulate heat effectively.
Parts commonly replaced
- Circulation pump
- Pump wiring harness
- Control board
32:0 Your boiler has been forced to shut down its water circulation pumps by an external safety device or a control signal from your heating system's management unit.
Your boiler has been forced to shut down its water circulation pumps by an external safety device or a control signal from your heating system's management unit.
Parts commonly replaced
- External safety interlock
- System control module
- Wiring harness
34:0 Your boiler is receiving a constant request for heat from an external control or thermostat, causing all the pumps to run continuously.
Your boiler is receiving a constant request for heat from an external control or thermostat, causing all the pumps to run continuously.
What to check first
- Check all room thermostats are not set excessively high
- Check if the programmers or timers are stuck on an 'Always On' setting
- Turn the boiler power off and back on at the fused spur to see if the signal resets
Parts commonly replaced
- External Room Thermostat
- Wiring Centre
- Control PCB
Related codes
35 Your boiler has failed to ignite or stay lit, meaning your heating and hot water have stopped working.
Your boiler has failed to ignite or stay lit, meaning your heating and hot water have stopped working.
What to check first
- Check if your gas supply is active by testing another gas appliance like a hob.
- Try resetting the boiler using the 'R' or reset button on the control panel.
- Ensure your system pressure is between 1.0 and 1.5 bar on the pressure gauge.
Parts commonly replaced
- Ionisation Electrode
- Ignition Lead
- Gas Valve
- PCB
Related codes
38 Your boiler has stopped working because it can no longer accurately measure the temperature of the water inside the system.
Your boiler has stopped working because it can no longer accurately measure the temperature of the water inside the system.
Parts commonly replaced
- Boiler water temperature sensor (NTC thermistor)
- Connecting cable harness
Related codes
38:0 Your boiler is reporting a normal status update rather than a failure, indicating that the internal burner control system is currently operating correctly.
Your boiler is reporting a normal status update rather than a failure, indicating that the internal burner control system is currently operating correctly.
What to check first
- Check if the display returns to the home screen manually
- Perform a simple reset if the code persists on the display
- Monitor for any other numerical codes that may appear alongside it
40 Your boiler has stopped working because it thinks the hot water tank is dangerously overheating due to a faulty electrical sensor.
Your boiler has stopped working because it thinks the hot water tank is dangerously overheating due to a faulty electrical sensor.
Parts commonly replaced
- Cylinder temperature sensor (NTC)
- Sensor wiring harness
Related codes
Showing 51–60 of 108
48 Your boiler has stopped heating your hot water because it can no longer detect the temperature of your hot water cylinder.
Your boiler has stopped heating your hot water because it can no longer detect the temperature of your hot water cylinder.
Parts commonly replaced
- NTC Cylinder Temperature Sensor
- Wiring Harness
Related codes
50 Your boiler has stopped providing hot water because the internal sensor that measures water temperature has detected a technical fault or a short circuit.
Your boiler has stopped providing hot water because the internal sensor that measures water temperature has detected a technical fault or a short circuit.
Parts commonly replaced
- DHW Temperature Sensor (NTC thermistor)
- Connecting cable harness
Related codes
51 Your boiler has stopped working because a sensor that monitors the water temperature has developed an electrical fault.
Your boiler has stopped working because a sensor that monitors the water temperature has developed an electrical fault.
Parts commonly replaced
- Outlet temperature sensor (NTC thermistor)
- Wiring harness
Related codes
58 Your boiler has stopped providing hot water because the internal sensor that measures water temperature is broken or disconnected.
Your boiler has stopped providing hot water because the internal sensor that measures water temperature is broken or disconnected.
Parts commonly replaced
- Domestic Hot Water (DHW) temperature sensor
- Wiring harness
Related codes
59 Your boiler has stopped working because it cannot accurately measure the temperature of the water leaving the unit, usually due to a fault in a sensor or its wiring.
Your boiler has stopped working because it cannot accurately measure the temperature of the water leaving the unit, usually due to a fault in a sensor or its wiring.
Parts commonly replaced
- Outlet temperature sensor
- NTC thermistor
- Wiring harness
Related codes
60:20 Your boiler is getting too hot while trying to heat your water, which usually means the heat isn't being transferred to your hot water tank quickly enough.
Your boiler is getting too hot while trying to heat your water, which usually means the heat isn't being transferred to your hot water tank quickly enough.
Parts commonly replaced
- Plate heat exchanger
- Diverter valve
- Temperature sensor
- Secondary pump
Related codes
77:1 Your boiler's internal communication system has detected an issue or a duplicate identity on its data network, which can sometimes happen after a power cut or part change.
Your boiler's internal communication system has detected an issue or a duplicate identity on its data network, which can sometimes happen after a power cut or part change.
What to check first
- Locate the 'Reset' button or menu option on the control panel.
- Perform a full system reset as per the user manual.
- Turn the power off at the fused spur switch for 30 seconds, then turn it back on.
Parts commonly replaced
- LON communication module
- PCB (Main control board)
Related codes
92 Your solar heating system has a faulty sensor or a wiring problem that is preventing it from correctly monitoring the temperature of the roof panels.
Your solar heating system has a faulty sensor or a wiring problem that is preventing it from correctly monitoring the temperature of the roof panels.
Parts commonly replaced
- Solar collector temperature sensor (NTC)
- Sensor wiring harness
Related codes
93 Your boiler has detected a technical fault with a sensor in your solar heating system, which may affect its ability to heat your water using solar energy.
Your boiler has detected a technical fault with a sensor in your solar heating system, which may affect its ability to heat your water using solar energy.
Parts commonly replaced
- Solar cylinder temperature sensor
- Sensor wiring harness
Related codes
94 Your boiler has lost communication with the temperature sensor in your hot water tank because of an electrical fault, meaning it cannot accurately monitor your solar heated water.
Your boiler has lost communication with the temperature sensor in your hot water tank because of an electrical fault, meaning it cannot accurately monitor your solar heated water.
Parts commonly replaced
- Cylinder temperature sensor (NTC)
- Sensor wiring harness
Related codes
Showing 61–70 of 108
A2 Your boiler has sensed that the internal pump is malfunctioning or water is not circulating correctly, which has caused the system to stop as a safety precaution.
Your boiler has sensed that the internal pump is malfunctioning or water is not circulating correctly, which has caused the system to stop as a safety precaution.
Parts commonly replaced
- Circulation pump
- Internal pump head
- Control PCB
Related codes
A5 Your boiler has detected that the water pump is likely stuck or not moving water correctly, which means the system cannot heat up safely.
Your boiler has detected that the water pump is likely stuck or not moving water correctly, which means the system cannot heat up safely.
Parts commonly replaced
- Internal circulation pump
- Pump motor head
- Main PCB
Related codes
A5:0 Your boiler has detected that the water pump responsible for circulating heat to your radiators is not behaving as expected, which may result in your heating not working correctly.
Your boiler has detected that the water pump responsible for circulating heat to your radiators is not behaving as expected, which may result in your heating not working correctly.
Parts commonly replaced
- Circulation pump
- Pump control cable/wiring harness
- PCB
A5:5 Your boiler has temporarily stopped the heating pump to prevent it from running unnecessarily, which is a normal part of its energy-saving settings.
Your boiler has temporarily stopped the heating pump to prevent it from running unnecessarily, which is a normal part of its energy-saving settings.
Related codes
A7 Your boiler's control panel has developed a communication fault and is unable to send or receive correctly.
Your boiler's control panel has developed a communication fault and is unable to send or receive correctly.
Parts commonly replaced
- Programming unit
- User interface (HMI)
- Control PCB
Related codes
A8 Your boiler's main internal computer has lost touch with the display panel, meaning the controls cannot talk to the heating unit.
Your boiler's main internal computer has lost touch with the display panel, meaning the controls cannot talk to the heating unit.
Parts commonly replaced
- Control Unit PCB
- HMU Programming Unit
- Internal Ribbon Cable
Related codes
b0 Your boiler has detected an electrical fault with the sensor that monitors the temperature of the exhaust gases, causing the system to shut down for safety.
Your boiler has detected an electrical fault with the sensor that monitors the temperature of the exhaust gases, causing the system to shut down for safety.
Parts commonly replaced
- Flude gas temperature sensor (NTC)
- Wiring harness
Related codes
b1 Your boiler's main control panel is having trouble talking to its own internal computer, meaning you cannot change settings or control the heating properly.
Your boiler's main control panel is having trouble talking to its own internal computer, meaning you cannot change settings or control the heating properly.
What to check first
- Locate the main power switch for the boiler (usually a fused spur on the wall).
- Turn the power off, wait for 60 seconds, and turn it back on to reboot the system.
- Ensure the control panel is pushed firmly into its housing if it is a removable type.
Parts commonly replaced
- Programming unit
- Main PCB (Control board)
- Wiring harness
Related codes
b4 Your boiler has encountered an internal electronic communication error that is preventing it from monitoring its own performance correctly.
Your boiler has encountered an internal electronic communication error that is preventing it from monitoring its own performance correctly.
Parts commonly replaced
- Printed Circuit Board (PCB)
- Electronic Control Box
Related codes
b5 Your boiler has experienced an internal communication error or processor glitch that is preventing it from running properly.
Your boiler has experienced an internal communication error or processor glitch that is preventing it from running properly.
What to check first
- Locate the power switch or fused spur for the boiler
- Turn the power off, wait for 30 seconds, and turn it back on
- Press the 'Reset' button on the boiler control panel once
Parts commonly replaced
- Electronic Control Unit (PCB)
- Wiring harness
Related codes
Showing 71–80 of 108
b7 Your boiler's internal computer chip has been disconnected or has developed a communication fault, meaning the system doesn't know which settings to use.
Your boiler's internal computer chip has been disconnected or has developed a communication fault, meaning the system doesn't know which settings to use.
Parts commonly replaced
- Boiler Coding Card
- Ignition Control Circuit Board
Related codes
b8 Your boiler has detected a broken connection or a fault with the sensor that monitors the temperature of the exhaust gases, causing the system to stop working for safety.
Your boiler has detected a broken connection or a fault with the sensor that monitors the temperature of the exhaust gases, causing the system to stop working for safety.
Parts commonly replaced
- Flue gas temperature sensor
- Wiring harness
- Sensor clip
Related codes
bA Your boiler is having trouble communicating with the control box that manages your second heating zone, meaning that specific area may not heat up correctly.
Your boiler is having trouble communicating with the control box that manages your second heating zone, meaning that specific area may not heat up correctly.
Parts commonly replaced
- Mixer extension kit electronics
- KM-BUS communication cable
- Mixer motor
Related codes
bc Your boiler has lost its connection with the remote control unit used to manage your primary heating circuit.
Your boiler has lost its connection with the remote control unit used to manage your primary heating circuit.
What to check first
- Check if the batteries in your Vitotrol unit need replacing
- Ensure the remote control is correctly docked in its wall bracket
- Turn the boiler power off and back on at the fused spur to reset the connection
Parts commonly replaced
- Vitotrol 200/300 Remote Control unit
- Communication wiring
- Bus communication module
Related codes
bd Your boiler has lost connection with the remote control unit that manages your second heating zone, meaning you cannot adjust the temperature for that specific area.
Your boiler has lost connection with the remote control unit that manages your second heating zone, meaning you cannot adjust the temperature for that specific area.
What to check first
- Check if the Vitotrol remote unit is properly seated on its wall base
- Switch the boiler off at the fused spur, wait 30 seconds, and switch it back on to reset the connection
- Inspect the remote unit batteries (if applicable) or check for visible damage to the wiring leading to the unit
Parts commonly replaced
- Vitotrol 200/300 Remote Control unit
- Low voltage communication wiring
- LON communication module
Related codes
be Your boiler is having trouble communicating with the wall-mounted thermostat control because of a setup or configuration error.
Your boiler is having trouble communicating with the wall-mounted thermostat control because of a setup or configuration error.
Parts commonly replaced
- Vitotrol 200/300 Remote Control
- Control Unit PCB
- Communication Cable
Related codes
bF Your boiler is currently stuck in an automated filling process and cannot continue until this is resolved.
Your boiler is currently stuck in an automated filling process and cannot continue until this is resolved.
Parts commonly replaced
- External Filling Loop Valve
- Boiler Control Unit (PCB)
- Electronic Pressure Sensor
Related codes
C2 Your boiler is having trouble 'talking' to your solar panels or an additional heating control part, which might prevent those specific systems from working correctly.
Your boiler is having trouble 'talking' to your solar panels or an additional heating control part, which might prevent those specific systems from working correctly.
What to check first
- Locate the power switch (fused spur) for the boiler.
- Turn the power off, wait for 30 seconds, and turn it back on to see if the connection resets.
- Check if any external solar controllers or expansion boxes have lost power or been unplugged.
Parts commonly replaced
- KM-Bus connection cable
- SM1 Solar Control Module
- Internal expansion PCB
Related codes
C5 Your boiler is having trouble communicating with its internal pump, which means it cannot properly move heated water around your system.
Your boiler is having trouble communicating with its internal pump, which means it cannot properly move heated water around your system.
Parts commonly replaced
- Internal circulation pump
- Pump communication cable
- Main PCB
Related codes
C5:20 Your boiler has detected that the water temperature is currently lower than its minimum safety setting and is pausing to protect the system.
Your boiler has detected that the water temperature is currently lower than its minimum safety setting and is pausing to protect the system.
Parts commonly replaced
- Flow temperature sensor
- NTC sensor
Showing 81–90 of 108
C6 Your boiler is having trouble communicating with the internal pump that moves hot water around your heating system.
Your boiler is having trouble communicating with the internal pump that moves hot water around your heating system.
Parts commonly replaced
- Variable speed pump
- Pump communication cable
- Main PCB
Related codes
C6:75 Your boiler has detected that the water temperature is too hot and has automatically limited it to prevent damage to your heating system.
Your boiler has detected that the water temperature is too hot and has automatically limited it to prevent damage to your heating system.
Parts commonly replaced
- Flow temperature sensor
- Heat exchanger
- PCB
C7 Your boiler is having trouble communicating with the internal pump that moves hot water through your radiators, which may prevent your heating from working correctly.
Your boiler is having trouble communicating with the internal pump that moves hot water through your radiators, which may prevent your heating from working correctly.
Parts commonly replaced
- Internal circulation pump
- Wiring harness
- Main PCB
Related codes
Cd Your boiler has lost its connection to the remote control or internet monitoring system, so you may not be able to adjust settings via your app or external thermostat.
Your boiler has lost its connection to the remote control or internet monitoring system, so you may not be able to adjust settings via your app or external thermostat.
What to check first
- Check that your internet router is switched on and working
- Ensure the Vitocom 100 communication module is firmly plugged into the boiler
- Turn the boiler power off and back on again to restart the communication link
Parts commonly replaced
- Vitocom 100 LAN/WLAN module
- Connecting cable
Related codes
CE Your boiler is having trouble communicating with an add-on control or an external smart home accessory, which may affect its ability to run efficiently.
Your boiler is having trouble communicating with an add-on control or an external smart home accessory, which may affect its ability to run efficiently.
What to check first
- Check if any external smart thermostats or controllers are turned on and have battery power.
- Restart the boiler by turning the power off and back on at the fused spur switch.
- Ensure any wireless hubs or range extenders nearby are plugged in and working.
Parts commonly replaced
- External extension module (H5)
- Wiring harness
- OpenTherm gateway
Related codes
CF Your boiler is having trouble 'talking' to its internal Wi-Fi or internet connection module, which may prevent you from controlling it via apps or external thermostats.
Your boiler is having trouble 'talking' to its internal Wi-Fi or internet connection module, which may prevent you from controlling it via apps or external thermostats.
What to check first
- Turn the boiler off at the main power switch for 30 seconds, then turn it back on to reboot the electronics.
- Check your home internet router is working correctly and within range of the boiler.
- Verify that any external smart thermostats or bridges are powered on and connected.
Parts commonly replaced
- Communication module (WiFi/LAN)
- Electronic controller (PCB)
Related codes
d3:14
This code is simply an information display showing the current heating settings rather than an actual fault with your boiler.
d4:0 Your boiler's heating control settings have been reset to zero, meaning it does not currently know it needs to provide heating to your home.
Your boiler's heating control settings have been reset to zero, meaning it does not currently know it needs to provide heating to your home.
What to check first
- Access the boiler control panel menu
- Navigate to the Heating Curve settings
- Adjust the 'Level' or 'Shift' parameter to your desired comfort setting to reactivate the heating schedule
dA Your boiler has lost its connection to the indoor temperature sensor for your main heating area, meaning it cannot accurately tell how warm your rooms are.
Your boiler has lost its connection to the indoor temperature sensor for your main heating area, meaning it cannot accurately tell how warm your rooms are.
Parts commonly replaced
- Room temperature sensor
- Wiring harness
- NTC thermistor
Related codes
db Your boiler has lost the ability to monitor the temperature in your second heating zone because a sensor has developed an electrical fault.
Your boiler has lost the ability to monitor the temperature in your second heating zone because a sensor has developed an electrical fault.
Parts commonly replaced
- Room temperature sensor (NTC)
- Sensor wiring harness
Related codes
Showing 91–100 of 108
dE Your boiler has lost connection with the temperature sensor that controls your second heating zone, meaning it cannot properly regulate the temperature for that part of your home.
Your boiler has lost connection with the temperature sensor that controls your second heating zone, meaning it cannot properly regulate the temperature for that part of your home.
Parts commonly replaced
- Room temperature sensor (NTC)
- Sensor wiring harness
- M2 extension module
Related codes
E4 Your boiler has stopped working because it is not receiving the correct electrical power or an internal fuse has blown.
Your boiler has stopped working because it is not receiving the correct electrical power or an internal fuse has blown.
Parts commonly replaced
- Internal Fuses
- Electronic Control PCB
- Ignition Transformer
Related codes
E5 Your boiler has stopped working because it cannot confirm that a flame is burning safely, leading to a complete shutdown for your protection.
Your boiler has stopped working because it cannot confirm that a flame is burning safely, leading to a complete shutdown for your protection.
Parts commonly replaced
- Ionisation electrode
- Ignition lead
- Burner control unit
- Gas valve
Related codes
E6 Your boiler has stopped working because there is not enough water flowing through the system to keep it running safely.
Your boiler has stopped working because there is not enough water flowing through the system to keep it running safely.
What to check first
- Check the pressure gauge on the front of the boiler; if it is below 1.0 bar, top it up using the filling loop.
- Ensure all radiator valves are fully open to allow water to circulate.
- Gently bleed air from your radiators using a radiator key.
Parts commonly replaced
- Circulation pump
- Heat exchanger
- Flow sensor
Related codes
EL Your boiler is currently running an automatic air-purging program to remove air bubbles from the system and does not require a repair.
Your boiler is currently running an automatic air-purging program to remove air bubbles from the system and does not require a repair.
What to check first
- Wait approximately 20 minutes for the automated venting process to complete
- Check that the system water pressure is between 1.0 and 1.5 bar
- The code should disappear and be replaced by the normal temperature display once finished
Related codes
F0 Your boiler has experienced a serious internal brain failure and the main control board likely needs to be replaced.
Your boiler has experienced a serious internal brain failure and the main control board likely needs to be replaced.
Parts commonly replaced
- Main PCB (Control Unit)
- Wiring Harness
Related codes
F1 Your boiler has switched itself off because it has reached a dangerously high temperature, likely due to a lack of water or poor circulation.
Your boiler has switched itself off because it has reached a dangerously high temperature, likely due to a lack of water or poor circulation.
What to check first
- Check the pressure gauge and top up the water if it is below 1.5 bar
- Bleed all radiators to remove trapped air from the system
- Ensure all radiator valves and isolation valves are fully open
- Reset the boiler after checking water levels
Parts commonly replaced
- Circulation pump
- Flue gas temperature sensor
- Heat exchanger (flushing service)
Related codes
F2 Your boiler has shut down because it has detected it is getting too hot, which is usually caused by a lack of water or a circulation problem.
Your boiler has shut down because it has detected it is getting too hot, which is usually caused by a lack of water or a circulation problem.
What to check first
- Check the pressure gauge on your boiler and top up the water if it is below 1.5 bar
- Ensure all your radiator valves are open and not switched off
- Once the boiler has cooled down, press the 'Reset' button to see if the fault clears
Parts commonly replaced
- Circulation Pump
- Temperature Limiter (Overheat Thermostat)
- Wiring harness
Related codes
F3 Your boiler is detecting a flame when there shouldn't be one, so it has shut down for safety purposes to prevent a malfunction.
Your boiler is detecting a flame when there shouldn't be one, so it has shut down for safety purposes to prevent a malfunction.
Parts commonly replaced
- Ionisation electrode
- Ignition lead
- Burner control unit (PCB)
Related codes
F4 Your boiler has failed to light the flame, which means it cannot provide any heating or hot water until the issue is resolved.
Your boiler has failed to light the flame, which means it cannot provide any heating or hot water until the issue is resolved.
What to check first
- Check if other gas appliances in your home, like a hob, are working to confirm your gas supply is active.
- Ensure your gas meter has credit if you use a prepay meter.
- Press the Reset button on the boiler control panel once to see if the fault clears.
Parts commonly replaced
- Ignition Electrode
- Ionisation Lead
- Gas Valve
- Ignition Module
Related codes
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F7 Your boiler has stopped working because it cannot correctly detect the water pressure, causing the system to shut down for safety.
Your boiler has stopped working because it cannot correctly detect the water pressure, causing the system to shut down for safety.
Parts commonly replaced
- Water pressure sensor
- Pressure sensor wiring harness
Related codes
F8 Your boiler has detected a problem with the gas valve not closing correctly, so it has shut down the burner for safety.
Your boiler has detected a problem with the gas valve not closing correctly, so it has shut down the burner for safety.
Parts commonly replaced
- Gas valve assembly
- Cables and wire harness
- Control PCB
Related codes
F9 Your boiler has stopped working because the internal fan isn't spinning fast enough to safely start the heating process.
Your boiler has stopped working because the internal fan isn't spinning fast enough to safely start the heating process.
Parts commonly replaced
- Fan assembly
- Fan wiring harness
- PCB (Control board)
Related codes
FA Your boiler has failed to start properly and the fan is running constantly to clear out the system, preventing the heater from firing up.
Your boiler has failed to start properly and the fan is running constantly to clear out the system, preventing the heater from firing up.
Parts commonly replaced
- Fan motor
- Fan wiring harness
- Main control PCB
Related codes
Fd Your boiler's internal computer has crashed due to an ignition failure or electrical interference, preventing it from starting the burner.
Your boiler's internal computer has crashed due to an ignition failure or electrical interference, preventing it from starting the burner.
What to check first
- Press the reset button or turn the boiler off and back on at the fused spur switch
- Ensure large electronic devices or powerful wireless routers are not sitting directly next to the boiler
- Check if other gas appliances in your home are working to ensure gas is reaching the property
Parts commonly replaced
- Ignition electrodes
- Ignition leads
- Electronic control unit (PCB)
Related codes
FE Your boiler's internal computer has encountered a critical error or is having trouble communicating with its electronic security card, causing the system to shut down for safety.
Your boiler's internal computer has encountered a critical error or is having trouble communicating with its electronic security card, causing the system to shut down for safety.
Parts commonly replaced
- Coding Card
- Printed Circuit Board (PCB)
- Control Unit
Related codes
Filling Your boiler is currently in the process of being filled with water, and the control system is waiting for the pressure to reach the correct level before it can start working again.
Your boiler is currently in the process of being filled with water, and the control system is waiting for the pressure to reach the correct level before it can start working again.
What to check first
- Locate the filling loop (a flexible silver hose) underneath your boiler or near your pipework.
- Gradually open the valves on the filling loop to allow water into the system.
- Monitor the pressure gauge on the front of the boiler until it reaches the green zone (typically between 1.0 and 1.5 bar).
- Close both valves firmly once the pressure is correct.
Venting
Your boiler is currently running a routine automated process to clear trapped air from its internal system.
Status & diagnostic codes 2 operating states & engineer diagnostics
Not faults — these are normal operating states. Tap to expand.
2 operating states & engineer diagnostics
Not faults — these are normal operating states. Tap to expand.