−II− Low

Boiler Fault Code −II−

Also written as II — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code −II− 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 is currently running a 15-minute cleaning and safety cycle to fill up its internal drainage system, which is a normal process after a power cut or reset. (As reported on Worcester Bosch R30 HE Plus)

Pick your boiler brand for the −II− fix

Worcester Bosch −II− 3 models

Source

Information for the −II− 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