203 Low

Boiler Fault Code 203

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code 203 appears across 2 boiler brands and 18 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is working correctly and is simply waiting for a signal from your thermostat or timer to start heating. (As reported on Worcester Bosch Greenstar 8000 Life & Style)

Pick your boiler brand for the 203 fix

Atag 203 2 models Worcester Bosch 203 16 models

Source

Information for the 203 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 7 July 2026