121 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
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Your boiler's internal computer brain is unable to talk to the front display panel, meaning the system cannot receive instructions to provide heating or hot water.
Your boiler has detected an internal electrical fault with a safety sensor involved in monitoring combustion, causing the unit to shut down to prevent unsafe operation.
Your boiler has detected a communication failure with a safety monitoring sensor, which prevents it from operating to ensure your protection.
Your boiler has detected an internal safety issue with the system that monitors combustion, causing it to shut down to prevent unsafe operation.
Your boiler has detected an inconsistency in how it monitors heat levels, causing it to shut down for safety reasons.
Your boiler has detected an issue with the sensor responsible for monitoring combustion levels, causing it to shut down for safety reasons.
Your boiler has detected an internal sensor fault that could affect the accuracy of its air-quality monitoring, meaning it has safely shut down to prevent incorrect operation.
Your boiler has detected an issue with the sensor responsible for monitoring combustion safety, which has triggered a precautionary shutdown to ensure your home remains safe.
Your boiler's internal sensor responsible for monitoring combustion safety is reporting an electrical reading that is outside of its expected normal range.
Your boiler has detected an internal electronic error with its safety monitoring system, meaning it can no longer accurately check for combustion issues.
Your boiler has detected a communication issue with a safety sensor responsible for monitoring combustion, which prevents the unit from operating safely.
Your boiler has detected an inconsistency with its internal air quality monitoring sensor, meaning the system cannot confirm it is operating safely so it has stopped working as a precaution.
Your boiler has detected an issue with the sensor responsible for monitoring combustion levels, meaning it cannot safely confirm that the heating process is running correctly.
Your boiler has detected an electrical issue with its internal carbon monoxide monitoring system, causing the safety system to shut down to prevent incorrect readings.
Your boiler has detected an electrical issue with the built-in sensor that monitors combustion, meaning it cannot safely confirm the boiler is running correctly.
Your boiler has detected an electrical reading error within its internal safety monitoring system, meaning it cannot accurately check the exhaust gases.
Your boiler has detected an electrical problem with a safety sensor that monitors gas combustion, meaning the unit will stop running to keep your home safe.
Your boiler has detected a communication issue with its internal air quality monitoring system, which prevents it from operating safely.
Your boiler has detected an issue with its internal safety monitoring system, which prevents the unit from operating correctly for your protection.
Your boiler has detected an inconsistency in its internal temperature readings, suggesting a potential issue with a safety sensor that prevents it from firing safely.
Your boiler has detected an internal issue with its safety monitoring sensor, which prevents it from operating to ensure your home remains safe.
Your boiler has detected an internal sensor error related to its safety monitoring system, which prevents it from operating normally to ensure your protection.
Your boiler has detected an issue with an internal sensor that monitors its combustion quality, meaning it has temporarily shut down for your safety.
Your boiler has detected an internal sensor error related to its safety combustion monitoring system, meaning it cannot reliably perform its own health checks.
Your boiler has identified an internal electronic memory error related to its safety monitoring system, meaning it can no longer guarantee safe operation.
Your boiler has detected a communication failure with an internal safety sensor, causing it to shut down to prevent unsafe operation.
Your boiler has detected that a safety sensor meant to monitor combustion quality is producing inconsistent readings, so it has stopped working for your protection.
Your boiler has detected a communication issue with its carbon monoxide monitoring sensor, meaning the safety system is not receiving the correct electrical signal.
Your boiler has detected an electrical issue with its internal safety monitoring system, which has automatically shut down the unit to ensure your home remains safe.
Your boiler has detected an internal sensor error related to its safety monitoring system, meaning it will likely shut down to prevent unsafe operation.
Your boiler's internal monitoring system has detected an electrical problem with the sensor responsible for checking combustion quality.
Your boiler has lost its connection to the sensor that measures the water temperature as it leaves the unit, meaning it cannot safely judge how much heat to provide.
Your boiler has lost the connection to the temperature sensor that tracks the flow of water, causing it to stop heating as a safety precaution.
Your boiler has stopped working because it cannot communicate with the sensor that monitors the temperature of the water returning to the unit.
Your boiler has stopped working because it has lost its connection to a sensor that measures the temperature of the water returning to the system.
Your boiler has lost the ability to read the temperature of your hot water supply, which means it has stopped providing hot water to your taps.
Your boiler has lost communication with the temperature sensor in your hot water tank, meaning it cannot accurately detect when your water is hot enough.
Your boiler has stopped working because it thinks the main water temperature sensor is broken or there is a problem with its internal wiring.
Your boiler has stopped working because it cannot correctly read the temperature of the water returning to the unit due to an electrical connection issue.
Your boiler has detected a faulty electrical signal related to the sensor that monitors your hot water temperature.
Your boiler has detected an electrical fault with the internal sensor that monitors the temperature of its hot water storage tank.
Your boiler has shut down because it has detected an unsafe increase in internal temperature, likely caused by a sensor fault or an issue with water flow.
Your boiler has stopped working because the water pressure is too low for it to operate safely.
Your boiler has detected that water isn't moving through the system fast enough, causing a large temperature difference that has triggered a safety shutdown.
Your boiler is overheating too quickly because water isn't flowing through the system correctly, often due to low pressure or trapped air.
Your boiler has detected an internal electrical connection issue that is preventing it from running safely.
Your boiler has detected an issue with the valve that controls the gas supply, meaning it cannot safely start up to provide heating or hot water.
Your boiler has detected a flame when there shouldn't be one, which has caused the system to shut down for safety.
Your boiler is failing to light the gas flame, meaning it cannot provide heat or hot water.
Your boiler has lost its flame while running and cannot manage to restart itself, likely due to a temporary interruption in the gas supply or a component failure.
Your boiler has detected a problem with the fan that safely pushes waste gases out of your home, causing the system to shut down for safety.
Your boiler has detected an issue with the airflow system, which means it cannot safely vent exhaust gases, so it has shut down to prevent any risk.
Your boiler is having trouble breathing because there may be a blockage, damage, or an obstruction in the pipework that vents exhaust gases outside.
Your boiler has lost the digital instructions telling it which type of gas it should be using, causing it to stop working for your safety.
There is a communication error between your boiler and its controls, often caused by an electrical wiring fault or a heavy load on the internal data connection.
Your boiler has detected an internal issue with its combustion monitoring system and has shut itself down to keep you safe.
Your boiler has detected an issue with the fuel-to-air balance that could affect safe operation, so it has safely shut itself down to prevent any risk.
Your boiler has detected that a key ignition component is wearing out, meaning it is struggling to reliably start the flame needed to heat your home.
Your boiler has detected a technical communication error between the main control board and the gas valve, preventing it from lighting safely.
Your boiler has detected a potential internal gas leak or an electrical failure that stops the gas supply from closing correctly, so it has shut down for safety.
Your boiler's internal computer brain has developed a memory error and can no longer process instructions correctly.
Your boiler has detected an electrical fault within its internal sensors or control board, which has caused the system to shut down for safety.
Your boiler’s internal computer brain is overheating, which has caused the system to shut down for safety.
Your boiler's main control board is receiving an incorrect electrical signal from the flame sensor, meaning the system cannot safely confirm if the burner is lit.
Your boiler is struggling to keep its internal flame lit steadily, which has caused it to shut down for safety reasons.
Your boiler’s internal computer boards are having trouble communicating because they haven't been properly synced or configured to recognize each other.
Your boiler has detected that a temperature sensor is sending a stuck or frozen reading, preventing it from heating your home or water safely.
Your boiler has detected that its temperature sensors are giving conflicting or incorrect readings, causing it to shut down for safety.
Your boiler's internal sensor that monitors water pressure has lost electrical contact or has failed, causing the system to stop working for safety.
Your boiler has detected an electrical issue with its internal water pressure sensor, meaning it cannot accurately tell if there is enough water in the system to run safely.
Your boiler has stopped working because it cannot detect the necessary change in pressure when the pump starts up.
Your boiler has detected a safety-related electrical fault within its internal wiring or a heat protection fuse, causing it to shut down to prevent damage.
Your boiler is struggling to remove excess water or is experiencing a communication error with an external safety part, causing it to shut down to prevent damage.
Your boiler is struggling because it has detected an external control unit connected for hot water, but the required safety link or sensor connection is missing.
Your boiler is having trouble communicating with the temperature sensor in your hot water storage unit, meaning your water might not heat up correctly.
Your boiler is struggling to heat your hot water tank effectively, causing it to time out before the water reaches the requested temperature.
Your boiler has detected a communication issue with the safety component that prevents internal corrosion, meaning it cannot confirm the tank is protected.
Your boiler is failing to detect a change in temperature when it tries to fire up, which usually means there is either not enough water circulating inside the system or a sensor isn't reading correctly.
Your boiler is confused because its temperature sensors are detecting heat patterns that do not match the expected flow of water, often caused by the sensors being swapped or losing contact with the pipes.
Your boiler is confused because its temperature sensors have likely been swapped or placed on the wrong pipes during installation or a recent repair.
Your boiler has lost the digital connection to its hot water storage tank, preventing the two units from communicating properly.
Your boiler's internal water flow sensor is struggling to detect movement, which prevents the unit from starting safely.
Your boiler is currently running a self-cleaning routine to remove trapped air bubbles from your pipes and radiators.
Your boiler is currently running an automated self-cleaning cycle to remove air bubbles from the pipes and is not experiencing a fault.
Your boiler is currently running a self-test at maximum power to ensure everything is working correctly after it has started up.
Your boiler is currently running a professional testing cycle to check it is functioning at full power after ignition, so no immediate action is required.
Your boiler is currently running a background test to check that it is burning gas correctly at its lowest possible setting.
Your boiler is currently performing a brief automatic test to ensure it can run safely at its lowest power setting.
Your boiler has entered a configuration mode that resets its internal central heating settings back to their original factory defaults.
Your boiler is currently running a programmed self-test to check that it can safely shut down if it gets too hot.
Your boiler is currently running a maintenance program to help fill or drain the system, meaning it has temporarily paused its normal heating and hot water functions.
Your boiler is currently in standby mode because it has not received an instruction from your thermostat to provide heating or hot water.
Your boiler is currently just in the process of starting up its internal air fan before it begins heating your home.
Your boiler is simply preparing its internal pump before starting the process of heating your radiators; this is a normal operational status, not a fault.
Your boiler is currently trying to light the flame to start heating your home or water.
Your boiler is currently performing a routine self-test or measurement, which is a normal part of its operational cycle.
Your boiler is simply finishing its normal cooling process after the heating has turned off, so there is no need to worry.
Your boiler's fan is currently running to clear out any leftover gases after a heating cycle, which is a normal part of the cooling-down process.
Your boiler is perfectly healthy and is simply circulating water around your radiators after the heating has switched off to ensure the system cools down safely.
Your boiler is perfectly fine; it is currently in a brief, mandatory rest period to prevent the system from turning on and off too frequently.
Your boiler is currently performing a routine self-check to ensure it is burning fuel efficiently, and this usually only lasts for a few moments.
Your boiler is currently running a brief internal testing sequence to check hot water settings and will return to normal operation by itself.
Your boiler is preparing to heat your tap water by moving the pump into position; this is a normal operational state and not an actual fault.
Your boiler is currently running an internal testing procedure for your hot water system and is not actually broken.
Your boiler is temporarily pausing because its internal safety sensors detect that the airflow needed to burn fuel safely is not moving correctly.
Your boiler has temporarily stopped because it cannot get the internal fan spinning at the correct speed to safely clear exhaust gases.
Your boiler has temporarily shut down because an external safety device, such as a condensate pump or an overheat sensor, has told it to stop running to prevent damage.
Your boiler has detected a minor hiccup and is running in a limited mode to keep you warm while it monitors itself.
Your boiler is struggling to keep its flame steady while running at a very low power setting and has temporarily shut down to protect itself.
Your boiler is undergoing a mandatory safety check of its internal air quality sensors and is briefly pausing to ensure it is operating safely.
Your boiler has detected high levels of carbon monoxide and has automatically paused operation to keep you safe while it waits for the fumes to clear.
Your boiler is currently taking a short break to automatically re-calibrate its internal settings, during which it will temporarily pause heating and hot water production.
Your boiler has detected unusual airflow patterns, likely caused by strong winds outside, and has temporarily limited its heat output to keep the system stable and quiet.
Your boiler is temporarily pausing because it cannot detect enough water flowing through the system to heat it safely.
Your boiler has detected that the water level inside the heating system has dropped too low and needs to be topped up to function correctly.
Your boiler has detected an issue with its internal combustion chamber and has entered a protective standby mode to prevent damage.
Your boiler is currently running an automated air-removal cycle to clear trapped air from the system, which is a normal process after maintenance or a power restart.
Your boiler is currently running an automatic internal test to check that water is flowing correctly through the system.
Your boiler is currently running an internal calibration check and is simply waiting for a few more minutes to complete its automatic system health test.
Your boiler is currently performing an automatic internal check and is not experiencing a fault.
Your boiler is simply reminding you that it is time for its scheduled annual safety check and service.
Not faults — these are normal operating states. Tap to expand.
BoilerFaultCodes