Your boiler is currently running a self-cleaning cycle to remove air bubbles from the pipes and will return to normal operation shortly.

To activate the venting function

What causes this fault?

This code appears when the boiler detects that it needs to purge trapped air from within the heat exchanger or pipework to ensure efficient operation. It is often triggered automatically after the system has been refilled or if internal sensors detect air bubbles that could lead to overheating. The boiler isn't broken; it is simply performing a routine maintenance cycle to protect its internal components.