Your boiler is operating normally and is currently in the process of starting up the burner to provide heat or hot water.

Burner ignited

What causes this fault?

This is not a fault, but rather a status message indicating that the boiler has successfully lit the flame. It confirms that the internal ignition sequence is complete and the unit is now producing heat for your radiators or hot water. You will see this code every time the boiler starts up as part of its normal, healthy operation.