Asus P9D-MV - Manual (Page 44)

2-24 Chapter 2: Hardware information
3 Locator LED (LOCLED1)
The Locator LED is a user-activated LED on the front of the server module
that can be remotely turned on or off. It is used to find a specific server
module within a chassis.
4. CPU Warning LED (ERR_CPU1)
The CPU warning LED lights up to indicate that a CPU error or failure has
occurred.