P.04 Low

Boiler Fault Code P.04

Also written as P04 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code P.04 appears across 3 boiler brands and 15 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is currently running a special testing mode designed for engineers to check the system's performance, which will automatically turn off on its own after fifteen minutes. (As reported on Glow-worm Easicom3 System)

Pick your boiler brand for the P.04 fix

Glow-worm P.04 11 models Sime P.04 1 model Vaillant P.04 3 models

Source

Information for the P.04 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