How much does it cost to fix boiler error code 4-b6?

Typical repair cost for the boiler 4-b6 fault is £0-80 including labour.

4-b6 Low

Boiler Fault Code 4-b6

Also written as 4B6 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code 4-b6 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 internal water temperature is very low and has activated its built-in frost protection mode to prevent freezing. (As reported on Worcester Bosch Greenstar 2000)

Pick your boiler brand for the 4-b6 fix

Worcester Bosch 4-b6 1 model

Source

Information for the 4-b6 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