BoilerFaultCodes L4 High
Boiler Fault Code L4
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code L4 appears across 2 boiler brands and 10 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has stopped working because it cannot correctly detect how much water is flowing through the system or what the temperature is. (As reported on Ideal Logic+ System)
Pick your boiler brand for the L4 fix
Source
Information for the L4 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 27 April 2026