BoilerFaultCodes L 04 High
Boiler Fault Code L 04
Also written as L04 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code L 04 appears across 1 boiler brand and 4 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has detected an issue with the sensor that monitors the temperature of the water leaving the unit, causing it to shut down as a safety precaution. (As reported on Ideal i-mini2 C24)
Pick your boiler brand for the L 04 fix
Source
Information for the L 04 fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026