Your boiler's internal clock has lost track of the correct time, which is usually a minor issue that doesn't stop your heating or hot water working.

DIY fix possible

Check that your heating and hot water are working normally, as this code usually doesn't affect them.Use the boiler's control panel to open the date and time settings (check the manual or menu for a clock or time option) and enter the correct date and time.Keep an eye on the clock over the next few days. If it resets again or the code returns, contact a Gas Safe registered engineer to check the clock's backup power and the control unit.