How much does it cost to fix boiler error code 4-b3?

Typical repair cost for the boiler 4-b3 fault is £0-80 including labour.

4-b3 Low

Boiler Fault Code 4-b3

Also written as 4B3 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code 4-b3 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 is notifying you that the settings for its automatic outdoor temperature sensors are incorrectly configured or out of their allowed range. (As reported on Worcester Bosch Greenstar 2000)

Pick your boiler brand for the 4-b3 fix

Worcester Bosch 4-b3 1 model

Source

Information for the 4-b3 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