BoilerFaultCodesWhat the manual says
Manufacturer manualFault history mode diagnostic code
From this model's manual
Verified against the Zanussi Ultra Plus Combi installation & service manual.
What causes this fault?
This code appears because the boiler has been manually put into 'Service Mode' by a person pressing specific buttons on the control panel. It is a deliberate setting used to force the burner to its maximum power so an engineer can test the gas pressure and emissions. It is not caused by a mechanical failure or a broken internal part.
DIY fix possible
Press and hold the 'Preheat' and 'i' buttons together for 5 seconds.Restart the boiler using the power dial or reset button to exit the test mode.The display should return to the standard temperature or 'D' / 'C' status.
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