BoilerFaultCodesYour boiler is briefly keeping the internal pump running after the heating has switched off to cool down the internal components.
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 system pump over run
What causes this fault?
This occurs because the boiler needs to dissipate residual heat from the internal heat exchanger once the heating or hot water demand has met its target. The system purposefully keeps the pump spinning for a few minutes to circulate water and prevent the internal components from overheating. It is a normal safety function of the boiler's operating cycle rather than a mechanical failure.
DIY fix possible
No action is required as this is a normal operational status code.Wait for a few minutes for the 'd.1' code to disappear automatically.Ensure your radiator valves are open to allow heat to dissipate.
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 d.1 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Vaillant ecoMAX is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
Affiliate links — we may earn a commission at no extra cost to you.