45 -- 45 Low

Boiler Fault Code 45 -- 45

Also written as 4545 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code 45 -- 45 appears across 1 boiler brand and 2 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 in a restricted low-power mode, likely because it is performing a specific system test or an automated diagnostic check. (As reported on Worcester Bosch Greenstar R29 40 HE)

Pick your boiler brand for the 45 -- 45 fix

Worcester Bosch 45 -- 45 2 models

Source

Information for the 45 -- 45 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