Diagnostic Led - Dell Precision 7520 Owner's Manual

When you notice screen abnormalities like flickering, distortion, clarity issues, fuzzy or blurry image, horizontal or vertical lines,
color fade etc., it is always a good practice to isolate the LCD (screen) by running the Built-In Self Test (BIST).
How to invoke LCD BIST Test
1. Power off the Dell laptop.
2. Disconnect any peripherals that are connected to the laptop. Connect only the AC adapter (charger) to the laptop.
3. Ensure that the LCD (screen) is clean (no dust particles on the surface of the screen).
4. Press and hold D key and Power on the laptop to enter LCD built-in self test (BIST) mode. Continue to hold the D key, until
the system boots up.
5. The screen will display solid colors and change colors on the entire screen to white, black, red, green, and blue twice.
6. Then it will display the colors white, black and red.
7. Carefully inspect the screen for abnormalities (any lines, fuzzy color or distortion on the screen).
8. At the end of the last solid color (red), the system will shut down.
Dell SupportAssist Pre-boot diagnostics upon launch, initiates an LCD BIST first, expecting a user intervention
NOTE:
confirm functionality of the LCD.

Diagnostic LED

This section details the diagnostic features of the battery LED in a notebook.
Instead of beep codes errors are indicated via the bicolor Battery Charge LED. A specific blink pattern is followed by flashing a
pattern of flashes in amber, followed by white. The pattern then repeats.
The diagnostic pattern will consist of a two digit number being represented by a first group of LED blinks (1 through
NOTE:
9) in amber, followed by a 1.5 second pause with the LED off, and then a second group of LED blinks (1 through 9) in white.
This is then followed by a three second pause, with the LED off, before repeating over again. Each LED blink takes 0.5
seconds.
The system will not shutdown when displaying the Diagnostic Error Codes. Diagnostic Error Codes will always supersede any
other use of the LED. For instance, on Notebooks, battery codes for Low Battery or Battery Failure situations will not be
displayed when Diagnostic Error Codes are being displayed:
Table 5. LED pattern
Blinking Problem Description
pattern
Ambe White
r
2 1 processor
2 2 system board, BIOS ROM
2 3 memory
2 4 memory
2 5 memory
2 6 system board; chipset
2 7 display
3 1 RTC power failure
3 2 PCI/Video
3 3 BIOS recovery 1
3 4 BIOS recovery 2
Suggested Resolution
processor failure
system board, covers BIOS corruption or ROM error
no memory/no RAM detected
memory failure/RAM failure
invalid memory installed
system board/ chipset error
display failure
coin-cell battery failure
PCI/Video card/chip failure
recovery image nor found
recovery image found but invalid
Troubleshooting 81