Your boiler is struggling to circulate water properly because it cannot communicate correctly with its internal water pump.

Service Function: Pump control mode

What causes this fault?

This code appears when the boiler has been manually put into a specific service setting by an engineer, which changes how the internal pump operates. It is caused by an installer navigating the diagnostic menu and leaving the pump control function active rather than returning it to the standard automatic setting. Because this is a configuration setting rather than a broken component, the boiler is simply waiting for a command to return to normal operation.