Your boiler is currently going through its routine process of lighting the flame to start heating your water.

Ignition sequence (heating operation)

What causes this fault?

This status code appears when the boiler is actively trying to light the gas burner to provide heating or hot water. It represents a normal part of the startup cycle where the internal computer checks the safety sensors before opening the gas valve and creating a spark. If this code stays on screen for a long time without the boiler firing up, it usually suggests a delay in the ignition process.