22 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's internal computer is unable to talk to its control panel, meaning the system cannot receive any instructions to turn on.
Your boiler has lost its connection to the external wall-mounted heating controller, meaning it no longer knows when to turn your heating on or off.
Your boiler has lost the digital connection between its main brain and the operating controls, causing it to stop functioning correctly.
Your boiler has stopped working because it cannot light the flame or clear its waste gases, which may be caused by a blocked flue or external venting issue.
Your boiler is struggling to breathe because the pipe that vents exhaust gases outside or draws in fresh air is blocked or damaged.
Your boiler has detected a flame inside when it should be turned off, which means it is shutting itself down as a safety precaution.
Your boiler has detected that it is getting too hot and has automatically switched itself off to prevent any damage to the internal components.
Your boiler has detected that the internal mechanism responsible for safely clearing exhaust gases is not working, so it has shut down to prevent unsafe operation.
Your boiler is struggling to detect enough water pressure to operate safely and has shut down to prevent damage.
Your boiler is struggling to detect the flow of water because a sensor inside the unit is not sending the correct signal.
Your boiler is struggling to accurately sense the temperature of your hot water, which means it cannot heat it reliably.
Your boiler is struggling to accurately measure the temperature of the water used for your taps and shower, so it has turned off this function to prevent overheating.
Your boiler is struggling to detect the movement of water, which means it has stopped heating your home or water to prevent internal damage.
Your boiler has detected that the water inside the system is getting far too hot, so it has shut down to prevent damage to itself.
Your boiler has detected that the water temperature difference between the pipes going out and coming back is abnormal, which usually indicates an internal circulation issue or a faulty temperature sensor.
Your boiler has lost its connection to the sensor that monitors the temperature of the water being sent to your radiators, causing the system to stop heating for safety.
Your boiler is unable to read the temperature of the water returning to it, so it has safely shut down to prevent overheating.
Your boiler has detected that the water returning from your radiators is far too hot, causing the system to shut down to prevent potential damage.
Your boiler has detected that the water temperature difference between the outgoing and incoming pipes is outside of the normal expected range, causing it to shut down to prevent damage.
Your boiler's internal computer is experiencing a software mismatch, meaning the control board does not recognise the installed firmware version.
The internal clock that schedules your heating and hot water has developed a fault, meaning the boiler cannot keep track of time or follow your programmed settings.
Your boiler is struggling to communicate correctly with your thermostat or external controls, so it has stopped heating to prevent errors.
Not faults — these are normal operating states. Tap to expand.
BoilerFaultCodes