Hello HW-U,   Was anything being done on the server when this occurred? Firmware updates or Hardware changes? Recently installed hardware or updated software may cause this exception. Update or remove the hardware or software.     In the log where you see "bus 4 device 0 function 1"; Is there an entry that indicates a slot number? A bus fatal error was detected on a component at slot # If so try reseating or removing the device.   Once you can complete POST without error; the BIOS 2.12.2 needs updated to 2.15.1 and check that the iDRAC is up to 5.10.50.00. [URL]  
I am getting the message below when rebooting a Dell PowerEdge R740xd2 server which has a BIOS version of 2.12.2 [IMAGE] This is message that I am getting in the iDRAC event log:        
The System Detected an exception during the UEFI pre-boot environment.