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Built-in self-test (BIST)
M-BIST
M-BIST (Built In Self-Test) is the system board's built-in self-test diagnostics tool that improves the diagnostics accuracy of
system board embedded controller (EC) failures.
NOTE:
M-BIST can be manually initiated before POST (Power On Self Test).
How to run M-BIST
NOTE:
M-BIST must be initiated on the system from a power-off state either connected to AC power or with battery only.
1. Press and hold both the M key on the keyboard and the power button to initiate M-BIST.
2. With both the M key and the power button held down, the battery indicator LED may exhibit two states:
a. OFF: No fault detected with the system board
b. AMBER: Indicates a problem with the system board
3. If there is a failure with the system board, the battery status LED will flash one of the following error codes for 30 seconds:
Table 18. LED error codes
Blinking Pattern
Amber
2
2
1
2
4. If there is no failure with the system board, the LCD will cycle through the solid color screens described in the LCD-BIST
section for 30 seconds and then power off.
LCD Built-in Self Test (BIST)
Dell laptops have a built-in diagnostic tool that helps you determine if the screen abnormality you are experiencing is an inherent
problem with the LCD (screen) of the Dell laptop or with the video card (GPU) and PC settings.
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.
NOTE:
Dell SupportAssist Pre-boot diagnostics upon launch, initiates an LCD BIST first, expecting a user intervention
confirm functionality of the LCD.
White
1
8
1
4
Possible Problem
CPU Failure
LCD Power Rail Failure
TPM Detection Failure
Unrecoverable SPI Failure
Troubleshooting
81
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