Your boiler has identified a temporary electronic error and is likely trying to restart itself automatically.

Temporary fault code (Refer to section 7.10)

What causes this fault?

This fault occurs when the boiler's control system encounters a momentary communication error or an unstable electrical signal. It is usually caused by the internal computer board failing to receive a clear confirmation that the burner has lit correctly, or a brief glitch in the electronic sequences. The boiler will typically attempt to clear this itself before deciding whether to stop completely.