If you have a problem such as a Boot Issue or a recurring Blue Screen.
It is always best to run diagnostics from a systems UEFI BIOS as it allows one to differentiate between problems caused by hardware failure and software issues. To access Lenovo UEFI Preboot diagnostics power down your Lenovo and tap [F10] repeatedly when powering it up:
The Preboot Diagnostics User Interface will now show:
It is always advised to Run All the tests:
Press the [↓] key until Run All is highlighted and press [Enter]:
It is recommended to run the extended tests:
Press the [↓] key until Extended Tests is highlighted and press [Enter]:
It will now take time to run the tests:
In my case all the tests pass meaning the blue screens this Yoga 14 (20DM) on a factory image of Windows 8 Upgraded to Windows 10 were more likely due to software and not the underlying hardware. If you have a hardware issue it should display an error message instead which you can contact Lenovo to rectify. I can press [Esc] to exit:
Then press the [→] and [↓] keys to highlight "Exit application" and press [Enter]:
In my case, as I have no hardware issue but a software issue, I am going to clean install Windows 10 Version 1809 on this system directly (opposed to a series of in place upgrade installs).
The Drive and Memory Modules are the parts most likely to fail however they are fortunately usually also the easiest to replace. Your can purchase a Solid State Drive or Replacement Memory Modules from Crucial using my affiliate link below. More details about looking for compatible parts and finding your Service Manual are available below: