Hi @jkm1986, 

Thank you for reaching out to us. Once you exit from diagnostics the system should reboot as normal. Do you experience this issue every-time you run the test? How do you exit from the diagnostics? Do you press the power button to restart the system or you clicked the exit button? 

If the issue is still present, then please share the LED status of the battery and hard drive we will be able to check what is causing the issue. You may refer https://www.dell.com/support/article/us/en/04/sln265807/dell-latitude-e6540-device-status-lights?lang=en for details on LED pattern. 

Dell-Tabassum M
Social Media Support
#IWork4Dell

This issue happens every-time I exit the diagnostics. I click exit button to leave the diagnostics.

Here's my YouTube video. I recorded Device Status LED's and Top Cover LED's behavior after leaving the diagnostics:

https://www.youtube.com/watch?v=phEJnQQvHgQ

Hello jkm1986,

Do you have any external peripherals connected to the machine? Try disconnecting all external devices and test. Update the BIOS to the latest from here. If the issue still remains you may need a replacement motherboard.