System Board Built-In Self-Test (M-Bist); Display Panel Power Rail Built-In Self-Test (L-Bist) - Dell Precision 7550 Service Manual

System board built-in self-test (M-BIST)

About this task
Steps
1. Press and hold both the M key and the power button to initiate M-BIST.
2. The battery-status light illuminates in amber when there is a system board failure.
3. Replace the system board to fix the issue.
NOTE: The battery status LED does not illuminate if the system board is functioning properly.

Display panel power rail built-in self-test (L-BIST)

About this task
Next steps
L-BIST (LCD Power Rail Test) is an enhancement to the single LED error code diagnostics and is automatically initiated during POST.
L-BIST isolates if the LCD is receiving power from the system board. L-BIST checks if the system board is supplying power to the LCD by
performing an LCD Power Rail test. If there is no power going to the LCD, the battery status LED flashes a [2,8] LED error code.
98 Troubleshooting