This is not an active fault code, but a menu setting used by engineers to view the history of previous problems with your boiler.

Last fault (displayed when a fault has occurred and navigating to service function 2.0)

What causes this fault?

This code appears when an engineer is accessing the boiler's internal memory to review its service history. It does not indicate a physical failure, but rather represents the 'mailbox' where the very last recorded error is stored for diagnostic purposes. If you see this, it simply means the system is being audited and there is no active mechanical breakdown currently triggered by this specific number.