BoilerFaultCodesThe 6 most common faults
01
Er 04 High DIY-safe
Your boiler is struggling to detect the water flowing through it, which is likely caused by low system pressure.
What to try first
Check your boiler pressure gauge; if it is below 1 bar, find the filling loop (usually a silver braided hose under the boiler).Open the valves on the filling loop to allow water into the system until the gauge reads 1.5 bar.Close the valves tightly and restart the boiler.
02
Er 01 High Engineer
Your boiler has failed to light the flame needed to heat your home and has safely shut itself down as a precaution.
Full guide for Er 0103
Er 02 High Engineer
Your boiler has detected that it is overheating and has shut itself down to prevent any damage or safety hazards.
Full guide for Er 0204
Er 03 High Engineer
Your boiler has stopped working correctly because the system has encountered a general safety error and has shut itself down to prevent damage.
Full guide for Er 0305
Er 05 High Engineer
Your boiler has detected an issue with the internal fan that pushes exhaust gases out of your home, so it has safely shut itself down to prevent operation.
Full guide for Er 0506
Er 06 High Engineer
Your boiler is struggling to accurately measure the temperature of the water used for your radiators, which has caused it to stop working to avoid potential damage.
Full guide for Er 06on the Biasi Advance Plus
Circulation pumpFlow switchPressure sensorIgnition electrodeGas valveIgnition lead
Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.
Call a Gas Safe engineer if…
- You can smell gas or see signs of a leak
- The Biasi shows an Emergency or High severity code
- The boiler keeps locking out after repeated resets
- You've tried the DIY checks and the fault hasn't cleared
- There's visible water leaking from the boiler
- The flame is yellow or orange instead of blue