BoilerFaultCodesSime ALL02 Fault Code
The Sime ALL02 fault code means: your boiler has stopped working because the water pressure is too low for it to operate safely.. It appears on 1 Sime model in our database.
Technical description: If the system pressure detected is lower than 0.5 bar, the boiler will stop and the display will show "ALL 02". To proceed increase the system pressure to between 1 and 1.5 bar.
DIY fix possible
Locate the filling loop (usually a silver flexible hose) underneath your boiler.Slowly open the valve or valves on the filling loop until you hear water flowing.Watch the pressure gauge on the boiler until it reaches between 1.0 and 1.5 bar, then close the valves fully.
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Sime models that show the ALL02 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Sime ALL02 fault code information on this page is sourced and cross-checked against the official Sime service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026