my dell latitude e6420 screen goes blank when it has to boot

guy i got the perfect answer

can you all see black screen when you upgrade biso and after that you see the other error "performing automatically IDE configuration and no boot drives are available?

so i got the solution

This laptop has a motherboard and a daughterboard.  In my case the USB is damaged on the daughterboard.  It's the USB next to the network port.  I ordered a replacement for the damaged board.  Got my fingers crossed that this is the issue.  I have the same issues listed in this thread, boot the laptop and the hard drive light will stop flashing and nothing happens.  Boot over and over and eventually if I'm lucky it would get to the OS load screen.  In general then it would boot but not always.  So reboot a few more times and IF the hard drive light keeps flashing eventually the OS would load.  So here is the really odd thing.  Just before it started never bootingg (always black screen) the head phone jack died.  The headphone jack is on that same board.  So now that I replace the motherboard for about $20 on ebay.  I am moving on to the daughterboard $10 on ebay.

The CPU is stable at 65 degrees.  Anyone on here that can get into the diagnostics, I'm curious what temperatures are you seeing?

It's going to be a few days before I get that board.  I'll let you all know if that is the fix.

One last thing that hard drive light that would flash for about 20 seconds then go dead (No Boot) or keep flashing (BOOT) that light is on the daugtherboard as well.

That little board is somehow critical to the BOOT cycle which is just bad design.

I changed out the daughterboard and my laptop boots immediately.  The problem is solved!  On close inspection of the daughterboard itself there is a tiny board mounted part that is loose.  Definately design flaw from the Chinese factory.  Thanks China : (  The part is called "Dell Latitude E6420 VGA / USB / RJ-45 Port IO Circuit Board for Intel Video - CYXNG"  I'm not sure what the part number is from Dell.  The one I ordered on Ebay was undamaged and like I said fixed the issue.  Downside, you have to completely disassemble the laptop to change this part.  Upside, it is fairly easy and parts people have a youtube post that will run you through the process.  

I lived with this issue for literally years.  I'm so happy it's fixed and I hope this helps someone out!!!!

Hí, i´m from Cuba i was having the same issue that everybody- i was able to go into the setup and surf for in it, change and i loaded to default. I was no able to boot even if i was able to enter into onetime boot setup and i was able to see the USB, the hard drive and the DVD-CD player. a friend has the same laptop and we used the hard drive with everything installed in his laptop but even like this IT DIDNT BOOT, IT KEEP GOING TO BLANK SCREEN.

OK we just decided to change the CPU from his laptop to mine and i solve the problem but when i put my CPU back again to my laptop everything was like in the begin, i bought a new CPU (second hand) and my laptop is working great now.

I SOLVE MY PROBLEM WITH 40 $.

Did anybody ever come up with an actual solution to this problem? I have tried unplugging the daughter board, but it does not work still. I cannot get to diagnostics mode.