BoilerFaultCodesBiasi Er 04 Fault Code
Also written as ER04 — same fault.
The Biasi Er 04 fault code means: your boiler has detected that water is not flowing properly around your heating system, usually because the pressure is too low or a pump has stopped working.. It appears on 9 Biasi models in our database.
Technical description: Faulty primary circuit (no water or absence of flow)
DIY fix possible
Check the pressure gauge on the front of your boiler; if it is below 1.0 bar, use the filling loop to top it up to between 1.0 and 1.5 bar.Ensure your heating controls and thermostat are calling for heat.Restart the boiler using the reset button or dial.
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Biasi models that show the Er 04 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Biasi Er 04 fault code information on this page is sourced and cross-checked against the official Biasi service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026