72 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
The fault code is already on your display
Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →
Tap any card for details
Your boiler has lost its connection to the temperature sensor, meaning it no longer knows how hot the water is and has stopped working to keep you safe.
Your boiler has lost the connection to the sensor that monitors the temperature of the water returning to the unit, causing it to stop working for safety reasons.
Your boiler has detected a communication issue with the built-in hot water storage cylinder temperature sensor.
Your boiler has lost communication with the built-in hot water storage tank sensor, which means it may struggle to provide consistent hot water.
Your boiler has stopped working because one of its internal sensors has developed an electrical fault and can no longer measure the temperature of the water leaving the unit.
Your boiler has detected an electrical fault with the sensor that monitors water returning from your radiators, causing the system to shut down for safety.
Your boiler has detected an electrical wiring or sensor fault related to how it heats your hot water cylinder.
Your boiler has detected a faulty electrical signal related to the internal hot water cylinder sensor.
Your boiler has detected that it is getting too hot and has automatically shut down to prevent damage or overheating.
Your boiler has temporarily stopped working because there is not enough water inside the heating pipes to run safely.
Your boiler has detected that the water inside it is heating up or moving much faster than expected, so it has shut itself down to prevent any damage.
Your boiler has detected that the water inside it is heating up much faster than it safely should, causing it to shut down to prevent damage.
Your boiler has detected that the gases it is producing are too hot to be safe, so it has automatically shut down to prevent damage.
Your boiler is unable to open the internal valve that supplies gas to the burner, meaning it cannot ignite to provide heat or hot water.
Your boiler has detected a signal that suggests a flame is present even when the burner is turned off, causing it to shut down for your safety.
Your boiler is trying to start but cannot get the flame to light or stay lit.
Your boiler was working but has suddenly turned off because the flame has gone out and it cannot manage to relight itself.
Your boiler has detected that the internal fan responsible for safely venting exhaust gases is not spinning, so it has shut down to prevent unsafe operation.
Your boiler has detected a blockage or issue with the pipe that brings in fresh air and removes exhaust gases.
Your boiler has lost its memory of which specific model it is, meaning it cannot operate safely without professional reconfiguration.
Your boiler has lost its internal communication signal, meaning the main control board and internal components can no longer properly talk to each other.
Your boiler has lost communication with a sensor that monitors the flow of air and gas, so it has safely shut down to prevent incorrect operation.
Your boiler has temporarily stopped working because it cannot properly measure the flow of air and gas needed for safe operation.
Your boiler has temporarily stopped working because it is not detecting enough gas supply to safely light the flame.
Your boiler has detected an issue with how it regulates the flow of gas and air inside, so it has temporarily locked itself out for safety.
Your boiler has detected an issue while trying to operate safely in its high-performance mode, so it has temporarily locked itself out to prevent any potential risks.
Your boiler has detected an issue with the control system that regulates the flow of gas.
Your boiler has detected an issue with how the gas valve shuts down, meaning it is safely locking itself out to prevent any potential risks.
Your boiler's computer memory has encountered a data corruption error, meaning it can no longer safely control the system's operation.
Your boiler has detected an internal electronics or temperature sensor issue and has safely shut down to prevent damage.
Your boiler has detected an internal issue with the temperature monitoring system and has shut itself down to prevent overheating or damage.
Your boiler has detected an internal communication error within its main control system, causing it to safely shut down.
Your boiler is struggling to keep the flame alight consistently, causing it to shut down for safety reasons.
Your boiler's internal computer has forgotten its identity settings, preventing it from starting up correctly.
Your boiler is not showing proper heating temperatures because a water temperature sensor has failed or given an incorrect reading.
Your boiler is temporarily locked out because the sensors measuring water temperature are sending mismatched or incorrect readings.
Your boiler's sensor is having trouble reading the internal water pressure, which means it has safely shut down to prevent damage until the issue is resolved.
Your boiler has detected that the water pressure inside the system is currently too high.
Your boiler is locking out because it cannot detect the water pressure rising when the internal pump starts up.
Your boiler has shut down because a safety sensor has detected that the internal heat exchanger is getting too hot.
Your boiler has detected an issue with the system that removes waste water or controls the exhaust gases safely.
Your boiler has lost communication with a sensor that monitors your hot water, which means it has stopped heating your water to prevent potential system damage.
Your boiler has detected an electrical fault with an internal sensor measuring the temperature inside the secondary heat exchanger.
Your boiler has detected an issue with the built-in hot water storage tank pump, which means you may have a problem with your hot water supply.
Your boiler has detected that the water temperature is not changing properly between the pipes when it fires up.
Your boiler has detected that the temperature sensors measuring water flow are giving conflicting readings, so it has stopped working as a safety precaution.
Your boiler has detected that two internal temperature sensors have likely been wired or clipped onto the wrong pipes during installation or previous maintenance.
Your boiler has lost the digital connection to its internal hot water storage tank, meaning it cannot properly coordinate heating the water for your taps.
Your boiler is having trouble communicating with the internal water storage tank, which means your hot water supply may be affected or inconsistent.
Your boiler has detected an issue while checking the gas supply type and has locked out to keep your home safe.
Your boiler has detected an issue during its automated gas quality and safety check, and has temporarily stopped working to keep you safe.
Your boiler is operating normally and is currently heating your radiators.
Your boiler is temporarily paused because your wall thermostat or heating controller is telling it not to send heat to your radiators.
Your boiler is simply in summer mode or not receiving a demand for heating from your thermostat.
Your boiler is temporarily pausing because the internal fan is not spinning at the correct speed needed to safely light the burner.
Your boiler has temporarily fired up its internal frost protection system to prevent the pipes from freezing during cold weather.
Your boiler has temporarily stopped heating because a safety device, such as a blocked condensate drain or a safety thermostat, has activated to prevent damage.
Your boiler has detected a minor issue and is running in a temporary backup mode to ensure you still have some heating and hot water.
Your boiler has too much water in the system, causing the pressure to rise to a level that is higher than recommended for safe operation.
Your boiler has temporarily stopped working because a safety device in the exhaust flue or the condensate removal system is signaling a blockage or fault.
Your boiler has temporarily stepped down its performance to keep running safely after the burner briefly went out.
Your boiler has temporarily paused heating because the water is not flowing properly through the system.
Your boiler has temporarily paused to protect itself because there is not enough water inside the system.
Your boiler is temporarily pausing its operation to allow internal parts to cool down or stabilize, which is a normal safety feature to prevent overheating.
Your boiler has temporarily reduced its power because it is detecting unusual air movement or wind pressure in the flue system, likely due to external weather conditions.
Your boiler has detected a mismatch between the type of gas it is set up to burn and the electronic settings on its main computer board.
Your boiler has detected that the gas and air mixture is outside of safe operating limits and has paused itself to prevent incomplete combustion.
Your boiler has detected an issue with the quality of the gas burning inside, meaning it has safely shut down to protect your home.
Your boiler has stopped working because the water pressure inside the heating system has dropped too low.
Your boiler is currently running a brief self-test on one of its internal temperature sensors, which temporarily pauses the heating.
Your boiler is currently running a brief self-test on its water pressure system and temporarily pausing heating until the check is complete.
Your boiler is temporarily running a self-test on its internal temperature sensors, which pauses your heating until the check is finished.
BoilerFaultCodes