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XPS 14 9440 Owner's Manual

LCD Power rail test (L-BIST)

L-BIST is an enhancement to the single LED error code diagnostics and is automatically initiated during POST. L-BIST will check the LCD power rail. If there is no power being supplied to the LCD (that is if the L-BIST circuit fails), the battery status LED flashes either an error code [2,8] or an error code [2,7].

NOTE:If L-BIST fails, LCD-BIST cannot function as no power will be supplied to the LCD.

How to invoke the L-BIST Test:

  1. Press the power button to start the computer.
  2. If the computer does not start up normally, look at the battery status LED:
    • If the battery status LED flashes an error code [2,7], the display cable may not be connected properly.
    • If the battery status LED flashes an error code [2,8], there is a failure on the LCD power rail of the system board, hence there is no power that is supplied to the LCD.
  3. For cases, when a [2,7] error code is shown, check to see if the display cable is properly connected.
  4. For cases when a [2,8] error code is shown, replace the system board.

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