How to identify beep codes:

When a laptop or computer first powers on, it goes through an initial set of diagnostic tests to make sure vital components are preforming correctly. These tests are called POST or Power On Self Test. When a test fails, the user is notified via POST codes, Light codes, or Beep codes. For diagnosing Beep codes you need to:

• Power on the laptop or restart it if it is already on.
• Listen to the number of consecutive beeps when the computer begins to boot. Restarting the laptop may be necessary and should not harm the laptop at this time.

Dell XPS 15 (L521X) Beep Codes
# of Beeps	Description	Possible Cause(s)
1	BIOS ROM checksum in progress or failure	System board failure, covers BIOS corruption or ROM errors.
2	No Memory (RAM) detected	Memory or Memory slot failure
3	chipset Error (North and South bridge error, DMA/IMR/Timer error) Time-Of-Day Clock test failure Gate A20 failure Super I/O chip failure Keyboard controller test failure	System board failure
4	Memory read / write failure	Memory failure
5	Real Time Clock (RTC) power fail	CMOS battery failure
6	Video BIOS test failure	Video subsystem failure
7	CPU Cache test failure	Processor failure or motherboard failure
8	LCD	LCD failure

Most Common Fixes:

• 1 Beep: Replace the motherboard / system board.
• 2 Beeps: Reseat the memory or replace the memory.
• 3 Beeps: Replace the motherboard / system board.
• 4 Beeps: Reseat the memory or replace the memory.
• 5 Beeps: Replace the CMOS battery.
• 6 Beeps: Reseat or replace the video card or replace the motherboard / system board.
• 7 Beeps: Reseat or replace the CPU or replace the motherboard.
• 8 Beeps: Reseat the LCD cable or replace the LCD screen.