The process would be:

When powering on the Lenovo device look for the option to interrupt the startup and access the boot menu.  This can be either Enter, F2, F10, F12 or similar as will be shown for a moment when the laptop is first powered on typically under the Lenovo logo.  Once in the Boot Menu press Tab to select Application Menu and arrow down to Lenovo Diagnostics and select it by pressing Enter.  Run full diagnostics (takes 10-45 mins generally) and report back any specific error code.