Your boiler is currently in the process of lighting its burner to start heating your home; this is a normal status message and not a fault.

DIY fix possible

Observe the boiler for a few minutes to see if the code changes to S.04 (Heating mode: Burner on).Check that your thermostat is calling for heat if the code remains for an extended period.No action is required if the boiler continues to provide heating and hot water normally.