BoilerFaultCodesYour boiler is temporarily running a self-diagnostic check to ensure everything is working correctly and will resume normal operation shortly.
This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.
Technical description: Internalautomatictestprogrammes
What causes this fault?
This code appears when the boiler’s internal computer performs a routine safety check to ensure all components are communicating correctly. It is not a breakdown, but rather a temporary pause where the system verify sensors and settings before firing up again. Unless the code remains on the screen for a long period, it simply means the boiler is double-checking its own health.
DIY fix possible
Wait for 10-15 minutes for the boiler to complete its cycleMonitor the display to see if it returns to a regular state (e.g., S.4 or S.0)If the code persists for over an hour, try a simple reset using the button with the flame/cross icon
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