34 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 detected that it is running too hot and has automatically shut itself down to prevent damage.
Your boiler is trying to start but cannot detect a flame, so it has safely shut itself down to prevent gas from building up.
Your boiler has detected that the gases leaving the exhaust flue are much hotter than they should be, causing the system to shut down for safety.
Your boiler's internal computer has encountered a critical error and can no longer process instructions, meaning the unit cannot operate.
Your boiler has detected an internal electronic error within its main control brain, preventing it from operating safely.
Your boiler's internal computer is experiencing a communication error, meaning it has safely shut down to prevent incorrect operation.
Your boiler is struggling to clear exhaust gases safely, so it has stopped working to prevent any risk of fumes entering your home.
Your boiler has stopped working because it cannot move the water around the system effectively.
Your boiler is failing to light the internal flame needed to produce heat and hot water, so it has shut down as a safety precaution.
Your boiler has detected that the water temperature is very low and has automatically switched on its internal pump to circulate water and prevent the pipes from freezing.
Your boiler has detected that the internal pipes are at risk of freezing and has temporarily locked out to prevent damage.
Your boiler has detected that water is not moving through the system properly, which is preventing it from heating your home safely.
Your boiler has detected that the water level inside the heating system is too low to operate safely.
Your boiler has lost the ability to detect that water is flowing through its internal pipes, which prevents it from firing up to heat your home or water.
Your boiler is currently unable to detect if water is moving through the system correctly, which has caused it to stop heating to prevent internal damage.
Your boiler has lost its connection to the temperature sensor that monitors the water returning to the system, meaning it can no longer accurately read how hot or cold the water is.
Your boiler has stopped working because it cannot correctly read the temperature of the water returning to it, as a sensor or its wiring is faulty.
Your boiler is struggling to detect the outside temperature because the cable connected to the outdoor weather sensor is either loose or broken.
Your boiler is receiving an incorrect signal from an optional temperature probe located outside your home, which may cause your heating to run less efficiently.
Your boiler is struggling to keep the burner flame stable, causing it to detach from the burner surface, which forces the system to shut down for safety.
Your boiler has detected a flame even though it is telling the gas supply to stay off, which is a safety fault that prevents the system from running.
Your boiler has detected an issue with its internal airflow system, which is preventing it from firing up safely.
Your boiler has detected that the internal fan is spinning too slowly, which means it cannot safely clear waste gases and has shut down to prevent a hazard.
Your boiler is struggling to read the temperature of your hot water cylinder, which means it cannot safely heat your water.
Your boiler is struggling to read the temperature of your hot water cylinder because a sensor has developed an electrical fault.
Your boiler has detected an issue with the sensor responsible for monitoring your hot water cylinder, which means it cannot accurately determine if your water is at the correct temperature.
Your boiler has lost its connection to the thermostat that measures the temperature in your home, so it doesn't know when to turn the heating on or off.
Your boiler is struggling to detect the room temperature correctly because of a wiring or connection error, which is preventing your heating from operating reliably.
Your boiler has detected that a safety sensor connected to your underfloor heating system is not sending a signal, which is preventing the system from operating correctly.
Your boiler has detected a disconnection in the sensor that monitors the air and gases flowing through your flue system, which prevents it from operating safely.
Your boiler has detected a faulty connection in the system that monitors the safe exit of exhaust gases, so it has shut down to ensure your home remains safe.
Your boiler has detected that the exhaust gases leaving the flue are hotter than they should be, causing it to shut down for safety.
Your boiler has lost the ability to send signals between its internal components, which means it has stopped working as a safety precaution.
Your boiler has been locked out because the reset button has been pressed too many times in a short period, and it now needs to be left alone to reset its internal memory.
BoilerFaultCodes