Asus P9D-E/4L - Manual (Page 44)

2-24 Chapter 2: Hardware information
3. CPU Warning LED (ERR_CPU1)
The CPU warning LED lights up to indicate that a CPU error or failure has occurred.
4. Power LED (+5V_LED1)
This LED lights up when the Power-on button is pressed and the system is on.
• The heartbeat LED functions only when you install the ASUS ASMB7 Management
card.
• Everytime after the AC power is replugged, you have to wait for about 60 seconds
for the system to power up.
The warning LED functions only when you install the ASUS ASMB7 Management card.