J Unknown

Boiler Fault Code J

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code J appears across 4 boiler brands and 4 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Pick your boiler brand for the J fix

Baxi J 1 model Main J 1 model Potterton J 1 model Worcester Bosch J 1 model

Source

Information for the J 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 31 August 2026