Manuals for the LCB-2 and TCBC boards categorize faults by system impact. Key codes often encountered include:

The OCSS (Operational Control Sub-System) cannot operate due to a critical driver fault.

Door malfunctions are the most frequent cause of service calls. Xizi Otis systems use specific routines for door management: Common Faults Of OTIS Elevator (including Analysis) - News

The door failed to close within the programmed time (typically 20s). This often points to obstructed tracks or faulty DCL (Door Close Limit) signals.