The boiler's internal timer has lost track of its heating schedule, so it may not switch on and off at the times you have set, but it is not usually a sign of danger.

DIY fix possible

Check the boiler display for any other fault codes and note them down.Reset the boiler by pressing the reset button on the control panel, or switch it off at the isolator or wall switch for one minute, then switch it back on.Check that the clock, date and heating programme on the controls are correct and set them again if needed.If the code returns or the heating and hot water still do not behave as scheduled, contact a Gas Safe registered engineer.