E4 High

Boiler Fault Code E4

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code E4 appears across 5 boiler brands and 10 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your heat pump has stopped making hot water because the sensor that monitors your cylinder's temperature is no longer communicating correctly. (As reported on Ideal HP290)

Pick your boiler brand for the E4 fix

Baxi E4 1 model Ideal E4 2 models Sime E4 2 models Viessmann E4 4 models Worcester Bosch E4 1 model

Source

Information for the E4 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