BoilerFaultCodesYour boiler is simply notifying you that it is currently busy heating your tap water and there is no actual fault.
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: Boiler is operating for DHW
What causes this fault?
This code appears when the boiler detects a demand for hot water from a tap or shower. It is a status indicator rather than a malfunction, showing that the internal components are currently prioritising your hot water over central heating. Once the tap is turned off, the code should disappear as the boiler returns to its normal standby or heating mode.
DIY fix possible
No action is required as this is a normal status message.Wait for the hot water tap to be turned off and the boiler will return to its normal standby or heating mode.
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A boiler cover plan would cover faults like C4 — no call-out fees, no surprises.
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