BoilerFaultCodesTechnical 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 is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.