52 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 is requesting its scheduled annual service or a routine maintenance check to ensure it continues to run safely and efficiently.
Your boiler's internal computer has lost touch with its control system, meaning it can no longer send signals to heat your home or water.
Your boiler has failed to light or maintain a flame, causing the system to shut down for safety.
Your boiler has detected a flame in the burner when there shouldn't be one, causing it to stop for safety.
Your boiler has tried to stay lit multiple times but the flame keeps going out, so it has shut down for safety.
The boiler's internal computer has detected a technical hardware failure during its startup checks and has shut down for safety.
Your boiler is struggling to confirm that a flame has been successfully lit, which prevents it from running for safety reasons.
Your boiler has failed a safety check related to how it detects the flame, meaning it cannot start up for your heating or hot water.
Your boiler has shut down because it has reached an unsafe temperature, triggered by a safety sensor that prevents the unit from overheating.
The boiler's internal computer has lost control over the flow of gas, causing the system to shut down for safety purposes.
Your boiler has stopped working because the internal fan, which safely exhausts fumes, is not spinning at the correct speed.
Your boiler has stopped working because the fan that removes waste gases cannot spin properly, causing the system to shut down for safety.
Your boiler has detected that the fan, which safely removes waste gases from the system, has stopped spinning or is blocked.
Your boiler has stopped working because the fan that helps push exhaust gases out of your home has broken or is spinning at the wrong speed.
Your boiler is struggling to clear air from the system before it starts up, which is usually caused by a blockage in the flue pipe or a technical fault with the internal fan.
Your boiler is struggling to breathe properly because something is blocking the pipes that carry exhaust gases outside.
Your boiler has detected that waste gases cannot properly escape through the flue pipe, causing the system to shut down for safety.
Your boiler is struggling to maintain a stable flame when running at a low power level, which is causing it to shut down for safety.
Your boiler is struggling to burn gas correctly when running at full power and has shut down for safety.
Your boiler has detected an unusual flame signal, which means it cannot safely confirm the burner is working correctly and has shut down as a precaution.
Your boiler has detected an ongoing internal issue that it cannot resolve automatically after trying several times.
Your boiler has temporarily paused because the water pressure inside the system has dropped too low.
Your boiler's internal water pressure sensor is reporting a fault, which has caused the system to shut down to prevent damage.
Your boiler has detected a blockage or a fault in the flue system that is preventing exhaust fumes from escaping safely at low power levels.
Your boiler has detected a blockage or restriction in the flue pipe that prevents exhaust fumes from escaping safely at high power.
Your boiler's main control board has detected an internal electronic failure and can no longer operate your heating or hot water safely.
Your boiler's main control computer is unable to talk to the fan, which means the system cannot safely clear exhaust gases and will not start.
Your boiler's internal computer brain is unable to talk to its control board, meaning the system cannot start or function safely.
Your boiler's computer system is currently confused and does not know how to correctly control your heating and hot water.
Your boiler has detected an internal communication error with the main control system, meaning it cannot safely regulate the burner.
Your boiler's central heating sensor has stopped communicating correctly, meaning the system doesn't know the temperature of your radiators and has shut down as a precaution.
Your boiler is shutting down because the water in the central heating circuit has reached an unsafely high temperature.
Your boiler has detected that the water temperature entering the system is too different from the temperature returning to it, suggesting the water isn't flowing through your pipes correctly.
Your boiler is struggling to open a gas valve properly, which is preventing the burner from lighting or staying on.
Your boiler has detected a problem with the temperature sensor that controls your main heating circuit, preventing it from managing the water temperature correctly.
Your boiler has stopped working because a sensor that monitors the temperature of the water returning to the unit has developed a fault.
Your boiler has shut down because the water returning from your radiators has become too hot, which usually points to a circulation problem.
Your boiler has detected that the water is not flowing through the system correctly, causing a temperature imbalance between the pipes going out and coming back in.
Your boiler has detected an internal communication error between its main control boards, meaning the system cannot coordinate its functions correctly.
Your boiler has detected a problem with the sensor that monitors exhaust gases, and it has shut down as a safety precaution.
Your boiler's main heating component is becoming blocked with debris or limescale, preventing the system from heating up properly.
Your boiler has failed its internal self-checking process and has shut down as a safety precaution.
Your boiler has tried and failed to automatically adjust its gas settings too many times and has now locked itself out for safety.
Your boiler has detected an issue with how the gas and air are mixing, prompting the system to shut down for safety.
Your boiler has failed its internal self-check to ensure it is burning gas efficiently and safely.
Your boiler has detected an issue with the air and gas mixture used for combustion and has shut down for safety.
Your boiler has failed an internal safety check during startup and has stopped running for your protection.
Your boiler's automatic gas control system has failed to calibrate properly, meaning it cannot safely regulate the fuel it needs to stay alight.
Your boiler has been manually reset too many times in a short period and has locked itself as a safety precaution.
Your boiler's internal computer parts are having trouble communicating because their software versions do not match.
Your boiler's internal computer system has detected a failure with its built-in clock, which may prevent your heating schedules from working correctly.
Your boiler has reached its programmed service interval limit and is simply reminding you that it is time for a professional maintenance check.
Monthly cover means no unexpected bills when your boiler breaks down.
Affiliate links. We may earn a commission at no extra cost to you.
BoilerFaultCodes