12 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 the temperature of the exhaust gases leaving the flue is too high, causing it to shut down for safety reasons.
Your boiler has failed to ignite the flame needed to heat your water and has safely shut itself down as a precaution.
Your boiler has lost track of how hot the water inside the heating system is because a temperature sensor has failed.
Your boiler's flue sensor is detecting a fault, meaning the system cannot accurately monitor the temperature of the exhaust gases, so it has safely shut down to prevent damage.
Your boiler is struggling to detect the temperature of the water it is trying to heat, so it has shut down to prevent overheating.
Your boiler has registered a general operational error, which is often used as an example code in troubleshooting guides rather than a specific fault.
Your boiler has temporarily stopped working because the water pressure inside the system has dropped too low.
Your boiler has detected that water is not flowing properly around your heating system, so it has safely shut down to prevent overheating.
Your boiler has temporarily stopped working because it has detected that the exhaust gases coming from the flue are too hot.
Your boiler has failed to ignite or lost its flame, meaning it has temporarily stopped producing heating and hot water for your home.
Your boiler has detected an issue with the internal fan that safely removes combustion gases, causing it to lock out for your safety.
Your boiler is struggling to get water moving around the system correctly before it attempts to fire up.
BoilerFaultCodes