BoilerFaultCodes L09 High
Boiler Fault Code L09
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code L09 appears across 1 boiler brand and 3 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler's internal computer brain is not communicating correctly with the rest of the unit and needs to be officially set up. (As reported on Ideal Logic Code Combi ESP1)
Pick your boiler brand for the L09 fix
Source
Information for the L09 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