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No POST after disabling the Microsoft United Extensible Firmware Interface (UEFI) Certificate Authority (CA) in the BIOS A Dell Pro Max laptop can fail to post displaying a light-emitting diode (LED) diagnostic error code. It flashes four amber and then four white LED pulses and then repeats. The error only occurs after changing the following settings in the BIOS: Enable the Discrete Graphics Controller Direct Output Mode setting under 'Display: Hybrid Graphics or Advanced Optimus' Disable the Enable Microsoft UEFI CA setting under 'Boot Configuration' This is affecting the following laptops: Dell Pro Max 14 Premium MA14250 laptop Dell Pro Max 16 Plus MB16250 laptop Dell Pro Max 16 Premium MA16250 laptop Dell Pro Max 18 Plus MB18250 laptop Note : The 4A4W flash code is not a listed Dell diagnostic error code for these products.
Under these BIOS settings, the discrete Graphics processor Unit (dGPU) does not work. The failure causes the PANEL_MONITOR pin to be in an abnormal state.
Note: Before starting the update, perform the following: Back up all personal data. For more information, refer to Back Up and Recovery . Connect the AC adapter. Updating the BIOS to version 1.4.2 or later on the computer resolves the issue. To download and install the BIOS, refer to the BIOS Update Guide . For a computer that is facing the No POST issue, perform either of the following steps before updating the BIOS. They display the splash screen and allow access to modify the BIOS: Press and hold down the power button for 30 seconds to reset the real-time-clock (RTC) Disconnect the laptop battery and allow the Microsoft UEFI CA BIOS setting to be reset Note : To avoid this issue in the future, ensure that the Microsoft UEFI CA BIOS setting is properly configured. Back to Top
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