Asus KGNH-D16 - Manual (Page 22)

2-4 Chapter 2: Hardware information
3. BMC LED (BMC_LED1)
The green heartbeat LED blinks per second to indicate that the ASMB4 is
working normally.
• The heartbeat LED functions only when you install the ASUS ASMB4.
• Everytime after the AC power is replugged, you have to wait for about 30
seconds for the system power up
2. CPU warning LED (ERR_CPU1, ERR_CPU2)
The CPU warning LEDs light up to indicate that an impending failure of the
corresponding CPU.