BoilerFaultCodesYour boiler is currently waiting for a signal from an external smart control or thermostat, meaning it is in a standby or communication phase rather than a 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: Digital regulator status
What causes this fault?
This code appears when the boiler is waiting for a command from your external thermostat or heating controls to start heating. It usually indicates that the target temperature has been reached or that there is a temporary communication gap between the smart controller and the boiler's internal computer. The boiler isn't broken; it is simply sitting in a 'ready' state until your sensors tell it that your home needs more heat.
DIY fix possible
Check that your room thermostat is turned up higher than the current room temperatureEnsure your external heating programmer is set to 'ON' or 'AUTO'Check the batteries in your wireless thermostat or smart controller
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A boiler cover plan would cover faults like D.90 — no call-out fees, no surprises.
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