Troubleshooting ThinkPad T450

[ondroid]

Hi everyone,
I've got ThinkPad T450 with the following symptoms:

After pressing power button:

• The power button lights up and stays lit for ~20 seconds
• Fan spins up immediately and spins for ~7 seconds
• Keyboard Lock buttons flash and then go dark
• Display goes from transparent to black within 3 seconds of pressing the power button and then goes to transparent again after the power LED turns off (panel shows no image, backlight is off)
• With VGA monitor I get no output either

I tried:

• Removing RAM from socket - this gives me 1-3-3-1 beep code as it should
• I measured all voltage lines (all voltages are normal)
  • VCC5M
  • VCC3M
  • VCCCPUCORE
  • VCC1R05AMT
  • VCC1R35A
  • VCC0R675B
  • VCC1R5B
• I measured the following signals on the board:
  • BPWRG
  • CPUCORE_PWRGD
  • MEPWRG
  • MPWRG
  • RSMRST
  • PLTRST
  • DRAMRST
  • VCCST_PWRGD
  • VR_READY
  • Maybe some more that I didn't write down
• I flashed BIOS downloaded from Lenovo site - no change
• I measured signals on the display, it seems to be ok (Gets 3.3v and 20v for backlight, HPD goes high when panel goes dark, DP-AUX does not have any data going through)

Board draws 6 to 13 watts from DC IN.
I'm out of ideas, any help appreciated.