X250 not booting after disabling AMT in BIOS

[ekchidiya]

Hi, my X250 has run like a champ for 4+ years now. Last night the Lenovo Solution Center recommended the Intel ME Components application which I installed. After reviewing the application, I went into the BIOS and disabled AMT. After selecting save and reboot, the system rebooted but it did not show anything on screen. Here is what happens - The power button lights up, the keyboard backlight comes on, the heatsink fan spins up and then the keyboard lights go out in a second following by the heatsink fan shutting down. All through this process I don't see anything, not even a flicker, on the screen. There is no Lenovo Thinkpad logo, no cursor, no error message, absolutely nothing.

P.S. - This model has two batteries apart from the CMOS. I am calling them internal (accessible only after removing back cover) and external (user replaceable). The CMOS battery is hidden beneath the internal battery but its connector to the motherboard is accessible even without removing the internal battery. It also has a small hole on the back panel which 'resets' the computer or something.

Troubleshooting attempted -

Removed the external battery, used a pin to hold the reset button down for 15 seconds, re-attached external battery, rebooted without power cable connected and then with power cable connected

Removed external battery, unplugged internal battery, unplugged CMOS battery, left for 15 mins and then rebooted after connecting everything back

Removed external battery, unplugged internal battery, unplugged CMOS battery, held down power button for 30 seconds, left everything unplugged overnight and the rebooted after connecting everything back and rebooted with the power cable connected

Removed external battery, unplugged internal battery, unplugged CMOS battery, unplugged HDD (only storage device), connected CMOS back after 5 minutes (left internal battery and external battery unplugged) and rebooting after connecting the power cable only

In all the above cases, the result is the same - power button lights up and stays on, keyboard backlight stays on for a second only, heatsink fank stay on for maybe 3 seconds only. There is absolute nothing on the screen at any point.

P.S. I now have the external+internal+CMOS batteries and HDD unplugged. The result is the same when trying to boot up with the power cable only. Nothing on screen and the backlight and fan switch off after coming on for a brief period. Another thing I noted, might be nothing, is that the moment i plug in the power cable, these things happen. I dont even need to push the power button for this outcome. I am not sure if that means anything.

Am I up the creek without a paddle?

[RealBlackStuff]

One more thing to try: remove all batteries plus the RAM module, then try to boot with only AC.
It should beep 1-3-3-1 if there is any life left in your mobo.

From the X250 Userguide:

If you select Enabled, Intel AMT (Active Management Technology) is configured
and additional setup items are provided in MEBx (Management Engine BIOS Extension) Setup.
If you select Permanently Disabled, you will never be able to enable it again.
Be cautious when you want to use this option.
Note: You can enter the MEBx Setup menu by pressing the Ctrl+P key combination in the Startup Interrupt Menu window.
To display the Startup Interrupt Menu window, press the black button or Enter key during the power-on self-test (POST).

[ekchidiya]

I tried with all storage, cmos and ram removed. Just plugged in power and rebooted. Nothing on screen, no beeps.