BoilerFaultCodesYour boiler has detected that the internal pump is not rotating at the correct speed to circulate water through your heating system.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Map pump step (heating - combi & system only)
What causes this fault?
This fault occurs when the boiler's control board expects the internal pump to be spinning at a specific speed but detects that it is struggling or stationary. The most common reasons are a build-up of sludge debris seizing the pump's internal components or an electrical failure in the pump's motor or wiring. Without the pump moving water away from the heat exchanger, the boiler shuts down to prevent internal overheating.
This issue often surfaces at the start of autumn when the heating is turned back on after being idle all summer, allowing debris to settle and seize the pump.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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 1.d — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
Affiliate links — we may earn a commission at no extra cost to you.