BoilerFaultCodesYour boiler is currently running a service test at its lowest power setting and this is a status indicator rather than a functional error.
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: To run the burner at minimum rate
What causes this fault?
This indicator appears when a heating engineer has manually activated the 'service link' or minimum rate test mode during a routine inspection. It signifies that the boiler is being forced to run at its lowest possible power setting so the technician can accurately measure gas pressures and combustion levels. It is not a breakdown, but rather a sign that the boiler is in a specific diagnostic state.
DIY fix possible
Wait for the service or commissioning process to finishTurn the selector knob to the 'Reset' position and then back to 'On'Restart the boiler by switching the power off and on at the fused spur
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like SL — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.