Dell XPS 13-9360 Service Manual page 90

Diagnostics
The computer POST (Power On Self Test) ensures that it meets the basic
computer requirements and the hardware is working appropriately before the
boot process begins. If the computer passes the POST, the computer
continues to start in a normal mode. However, if the computer fails the POST,
the computer emits a series of LED codes during the start-up. The system
LED is integrated on the Power button.
The following table shows different light patterns and what they indicate.
Light pattern
2,1
2,2
2,3
2,4
2,5
2,6
2,7
3,1
3,2
3,3
3,4
90
Problem description
CPU failure
System board: BIOS and ROM failure
No memory or RAM detected
Memory or RAM failure
Invalid memory installed
System board or chipset error
LCD failure
CMOS battery failure
PCI or video card or chip failure
Recovery image not found
Recovery image found but invalid