BoilerFaultCodes 88 H......4....... High
Boiler Fault Code 88 H......4.......
Also written as 88H4 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 88 H......4....... appears across 1 boiler brand and 1 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 that the temperature monitoring system for the exhaust gases is not reading correctly, which means the boiler will stop working to ensure safety. (As reported on Ideal Isar M30 / M100)
Pick your boiler brand for the 88 H......4....... fix
Source
Information for the 88 H......4....... 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