Your boiler is currently updating its internal settings and is showing this code to indicate it has been reset during its configuration process.

Display status after pressing RESTART during PCB programming

What causes this fault?

This code appears because the boiler's internal computer has just been reset or is going through a setup process. It physically signifies that the circuit board is checking its own software settings to ensure everything is configured correctly for your home. While it looks like a fault code, it is actually just a brief status update showing that the system is rebooting.