BoilerFaultCodesYour boiler is currently trying to light the flame to start your heating, which is a normal part of its startup sequence.
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: Heating mode: Ignition. The ignition for heating mode is activated.
What causes this fault?
This code appears when the boiler is actively trying to light the internal flame to provide heat for your radiators. It is a normal part of the startup process where the boiler sends a spark to the burner to get the system running. If this code stays on the screen for a long time without the heating starting, it may indicate a struggle to establish a stable flame.
This status is most frequently seen during the autumn and winter months when the heating system is first being called upon to run after being idle over summer.
DIY fix possible
Check that your gas supply is turned on at the meterEnsure your thermostat is calling for heatWait a few minutes to see if the status changes to a normal running code
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 S.03 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.