BoilerFaultCodesYour boiler is currently working perfectly and is simply telling you that it is busy heating your radiators.
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: Status code: product is working correctly (heating mode)
What causes this fault?
This code appears when the boiler’s internal controls have successfully triggered the burner to provide heat for your radiators. It is a normal status message indicating that the diagnostic system is monitoring a standard heating cycle. There is no physical fault; the boiler is simply confirming it is responding to your thermostat's request for warmth.
You will see this code much more frequently during the autumn and winter months when your central heating is scheduled to run regularly.
DIY fix possible
This fault may be fixable without an engineer. Check your manual first.
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.04 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.