BoilerFaultCodesTechnical description
Service Mode / Sequence indicator following SL
What causes this fault?
This code appears because the boiler has been manually placed into a high or low fire test mode, typically by an engineer during an annual service or safety check. It is not a mechanical failure, but rather a temporary override that allows a technician to measure gas pressures and performance. Once the technician finishes their tests or exits the menu, the boiler will return to its normal heating settings.
This code is more frequent during the summer or autumn months when homeowners typically book their annual boiler service or gas safety record inspections.
DIY fix possible
Locate the mode dial on the front of the boiler control panel.Turn the dial away from the 'Service' or 'Spanner' icon back to 'Auto', 'On', or your desired temperature setting.Restart the boiler by pressing the reset button if the display does not clear immediately.