Example implementations relate to automatic diagnostic mode to identify a potential cause of a boot problem of a system. In an example, the automatic diagnostic mode iteratively isolates subsystems of the system in coordination with a baseboard management controller. For each iteration of subsystem isolation, a system boot is executed while a subsystem is isolated. The system boot is monitored against a watchdog timer of the baseboard management controller to determine if the system boot is successful. If the system boot is successful, the isolated subsystem is marked as a potential cause of the boot problem of the system. If the system boot is unsuccessful, the automatic diagnostic mode continues to iteratively isolate the subsystems.