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 temporarily locked itself out for safety because it detected the water getting too hot too often.
Your boiler's main control unit has encountered a communication error and is unable to operate safely.
Your boiler is struggling to circulate water, likely because the internal pump is jammed or there is air trapped inside the system.
Your boiler has detected an issue with the sensor that monitors exhaust gases, so it has safely shut down to prevent incorrect operation.
Your boiler is struggling to accurately measure the temperature of the water being heated for your taps and shower.
Your boiler's internal computer has lost contact with the main control panel, preventing it from starting up correctly.
Your boiler's computer has detected a serious internal fault that prevents it from operating safely, requiring a qualified professional to inspect or replace the electronic control system.
Your boiler's internal fan isn't spinning fast enough to safely clear away exhaust fumes, causing the system to shut down for your protection.
Your boiler has detected that the internal fan is spinning too slowly to safely clear waste gases, so it has shut down as a precaution.
Your boiler's internal fan is spinning faster than it should, which has caused the system to shut down for safety.
Your boiler has stopped working because the internal component responsible for pushing air through the system is failing to start.
Your boiler has lost connection to the weather sensor outside, but it should still continue to keep your home warm using its backup settings.
Your boiler has temporarily stopped working because the water pressure inside the system has dropped too low.
Your boiler has lost communication with the device that tells it how much water is inside, so it has shut down to prevent damage.
Your boiler has temporarily stopped working because it has detected an incorrect temperature reading from one of its internal sensors.
Your boiler has lost its connection to an essential safety internal plug, meaning it currently cannot communicate correctly with its control system.
Your boiler has detected that your radiators are not transferring heat properly, causing the water returning to the unit to be much cooler than the water leaving it.
Your boiler has temporarily stopped working because it has detected an electrical fault with the sensor that measures the temperature of the water flowing through the system.
Your boiler has detected that hot water is flowing in the wrong direction or circulating incorrectly, meaning it cannot heat your home properly.
Your boiler is having trouble 'reading' the temperature of the incoming water, which is causing it to stop operating correctly to prevent a potential error.
Your boiler has detected that the water inside the system is getting much hotter than it should be, so it has shut itself down to prevent damage.
Your boiler has automatically shut down because a safety sensor detected that the temperature inside the exhaust pipe is dangerously high.
Your boiler has tried to light several times but has been unable to detect a flame, causing the system to shut down for safety.
Your boiler has detected that the exhaust gases are getting too hot, too quickly, so it has turned itself off to prevent internal damage.
Your boiler has detected that hot gases are building up inside the system while the water meant to be heating your home is staying cold, so it has safely shut down to prevent overheating.
Your boiler has temporarily stopped because the hot water inside the system has become much hotter than it should be.
Your boiler has detected that the water inside isn't warming up as expected after it fires up, so it has stopped trying to prevent potential damage.
Your boiler has detected an issue with the valve that controls the gas supply, meaning it has safely shut down to prevent any risk.
Your boiler has detected a safety signal inside before it has even attempted to light, so it has safely locked itself out to prevent starting.
Your boiler is still detecting a flame even though it has tried to turn the gas supply off, which is a safety concern that requires an engineer.
Your boiler has detected that a safety valve controlling the gas supply is not sealing properly, so it has safely shut itself down to prevent a gas buildup.
Your boiler is showing this code simply because the reset button was held down for too long or pressed by mistake, which has confused the internal software.
Your boiler has detected that the water pump is not running as expected, which prevents heat from circulating through your home.
Your boiler has detected that hot combustion gases are escaping outside of the flue pipe instead of safely venting outside, which triggers an automatic safety shutdown.
BoilerFaultCodes