Troubleshooting
Topics:
• Built-in self-test (BIST)
• System board built-in self-test (M-BIST)
• Display panel power rail built-in self-test (L-BIST)
• Display panel built-in self-test (LCD-BIST)
• Outcome
• SupportAssist diagnostics
• Running the SupportAssist diagnostics
• System diagnostic lights
• Recovering the operating system
• Flashing the BIOS
• Flashing BIOS (USB key)
• Backup media and recovery options
• WiFi power cycle
• Releasing Ethernet (RJ-45) cable
Built-in self-test (BIST)
About this task
There are three different types of BIST to check the performance of display, power rail, and system board. These tests are
important to evaluate if an LCD or System board needs a replacement.
1. M-Bist: M-BIST is the system board built-in self-test diagnostics tool that improves the diagnostics accuracy of system
board embedded controller (EC) failures. M-BIST must be manually initiated before POST and can also run on a dead
system .
2. L-BIST: L-BIST is an enhancement to the single LED error code diagnostics and is automatically initiated during POST.
3. LCD-BIST: LCD BIST is an enhanced diagnostic test that is introduced through Preboot System Assessment (PSA) on legacy
systems.
Table 19. Functions
M-Bist L-Bist
Purpose Evaluates the health condition of the
system board.
Checks if the system board is supplying
power to the LCD by performing an LCD
Power Rail test.
Trigger Press the <M> key and power button. Integrated into the single LED error code
diagnostics. Automatically initiated
during POST.
Indicator of fault Battery LED light with Solid Amber. Battery LED error code of [2,8] blinks
Amber x2, then pause, then blinks White
x8.
Repair instruction Indicates a problem with the system
board.
Indicates a problem with the system
board.
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