E03 High

Boiler Fault Code E03

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code E03 appears across 11 boiler brands and 50 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler's main control computer is experiencing a serious internal error and has stopped the system to prevent further issues. (As reported on Vokera Pinnacle)

Pick your boiler brand for the E03 fix

Alpha E03 16 models Ariston E03 5 models Baxi E03 2 models Biasi E03 7 models ECA E03 4 models Ferroli E03 4 models Johnson Starley E03 4 models Keston E03 4 models Potterton E03 2 models Vokera E03 1 model Warmhaus E03 1 model

Source

Information for the E03 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