BoilerFaultCodesSime ALARM 02 Fault Code
Also written as ALARM02 — same fault.
The Sime ALARM 02 fault code means: your boiler has detected that the water pressure is too low, which prevents it from heating up or providing hot water.. It appears on 2 Sime models in our database.
Technical description: Low system pressure — restore to 1.0–1.5 bar using filling loop
DIY fix possible
Locate the silver filling loop cable underneath your boiler.Slowly open the valve(s) to allow water into the system while watching the pressure gauge.Close the valve(s) firmly once the pressure gauge needle reaches between 1.0 and 1.5 bar.
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Sime models that show the ALARM 02 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Sime ALARM 02 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