XPS 15 9550 won't boot - power light turns on (white) no beep or light codes, no POST

Hello,

Was experiencing general issues with my windows profile after windows updates last patch Tuesday so I initiated a system restore and let it run today.  After completion laptop turned off (instead of rebooting?)

1. Pressing the power button: Power button turns white (on) for ~30 seconds, then laptop turns off (indicated by power button light)
   1. no fans
   2. no screen (back-light or otherwise)
   3. no POST codes - beep codes or light codes.  
   4. no other visible activity
2. During that period nothing else happens, unless I press the power button again. If I do this
   1. The fans spin up momentarily
   2. The system then powers off (as indicated by the white power light)

I've tried:

• Disconnect power/battery and hold power button (60 seconds)
• Power system on with just battery
• Power system on with just wall power
• Remove mSATA HD and repeat the above
• Disconnect video connector and repeat above
• Remove mPCI WiFi module and repeat above
• Completely disassemble and remove CMOS battery (tested at 3.1 VDC) for 60 seconds, reassemble and repeat above

All with no change in behavior

• I am able to get a light code 2 Amber / 3 White if I remove the RAM module (as expected)
• D + PWR diagnostics cycle successfully through a range of colors then nothing

Laptop is 2 months out of warranty.  Any help debugging the issue is appreciated!

XPS 15 9550 September 2016

Other notes:

• UEFI Secure Boot was enabled
• HD was bitlocker encrypted in Windows 10
• HD is currently removed and has not changed behavior

Thanks so much!

This Reddit article appears to be similar: https://www.reddit.com/r/Dell/comments/44v957/dell_xps_15_9550_black_screen/

Here's the XPS 15 9550 Service Manual:

http://downloads.dell.com/manuals/all-products/esuprt_laptop/esuprt_xps_laptop/xps-15-9550-laptop_service%20manual_en-us.pdf

And the blink codes: