Bootlooping Thinkpad X230i - No backlight - No image (schematics included)

[Romanizer]

Hello fellow Engineers and hobbyists,

A couple of days ago, I got a broken Thinkpad X230i from a friend, saying it was unfixable and he saved it from recycling.

Here is the problem:

When turning it on, it stays on for about 5 seconds and then turns off again. This repeats indefinitely and happened when battery and/or charger(20V Bench PSU) powered. While bootlooping, it shows no image on screen and the backlight is off, but The Keyboard light and the thinklight are both on.
I checked all rails: 20V DC-in, 5V, 3.3V. All are present. The only rail I could make out that is missing is the VCC_GFXCORE_I rail for the CPU's integrated GPU. I'm guessing its an i3-3310M.

The VCC_GFXCORE_I rail is provided by a VT1324SFCX, which in turn is controlled by a VT1318MFQX (schematics attached, see pages 79 & 80).

I tried injecting Voltage into the rail, to see if there were shorted caps, because my meter was measuring about 1.4 ohms. But no luck.
I noticed that the power management IC VT1318MFQX is sending a fault signal to the buck converter VT1324SFCX telling it to shutdown.

Does anyone have an idea to what is wrong with my newly acquired Thinkpad?

Any help is greatly appreciated!!

[Rasz]

lack of VCC_GFXCORE can be faulty bios, bad ram, etc, GPU is brought up late in boot process
but 1 ohm on gpu-vcore is too low, take off L29 and check which side is low resistance

or buy <$20 replacement motherboard
https://allegro.pl/oferta/plyta-glowna-lenovo-thinkpad-x230-core-i3-8079804809
https://allegro.pl/oferta/100-sprawna-plyta-glowna-lenovo-x230-gw-fv-7994395139
https://allegro.pl/oferta/plyta-glowna-i5-3320m-lenovo-x230-2325-8017430419
even $10 with fan controller defect https://allegro.pl/oferta/plyta-glowna-lenovo-x230-3320m-intel-slj8a-8118683212

personally I LOVE x220/x230 motherboards for small projects(home routers,nas,camera servers etc), they cost less than raspberry pee while delivering x10 the performance and IO. I usually buy ones with defects like one USB port blown for $5-10 including lower case (means comes with radiator/fan and often wifi/bt)

[Romanizer]

Thank you for your response!

I was guessing that the GPU might not come up after a couple of seconds after boot, but my scope was confirming that the VCC_GFXCORE was trying to turn on.

I can rule out bad ram, because I tested multiple sticks in various configurations. I'll take of L29 and try locating the short then.

I'll order a 'new' mainboard as a last resort, first I will see if i can fix it very cheap. If not the mainboard are super cheap aswell, i did not expect that.