BoilerFaultCodes Main circuit pressure - yellow High
Boiler Fault Code Main circuit pressure - yellow
Also written as MAINCIRCUITPRESSUREYELLOW — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code Main circuit pressure - yellow 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 water pressure is too low, which prevents it from heating up safely. (As reported on Biasi Gaia)
Pick your boiler brand for the Main circuit pressure - yellow fix
Source
Information for the Main circuit pressure - yellow 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