Service Manual

Troubleshooting
Topics:
• Built-in self-test (BIST)
•
LCD Built-in Self Test (BIST)
• Dell SupportAssist Pre-boot System Performance Check diagnostics
• Diagnostic LED behavior
• Diagnostic error messages
• System error messages
• Recovering the operating system
• Real-Time Clock (RTC Reset)
• Flashing the BIOS
• Backup media and recovery options
• WiFi power cycle
• Flea power release
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 21. 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 the 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.
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.
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