HP zbook 17 g3 - endless restarting pre-POST loop

[murko1]

Hello,
I have problem with the HP ZBOOK 17 G3. It suddenly wont fully start, instead it keeps in a power on/power off loop. The loop is:

•  power led button blinks quickly 2x and simultaneosly wifi + mute button blinks 1x + complete backlight for keyboard blinks 1x, after that the caps lock lights up for ~2sec -> see video
• front leds: wireless(orange) + power(white) + drive(orange) blink once at same time, then battery led blinks 5x - (changing orange/white) -> see video
• side led is solid white when AC charger connected
• during this process both fans (cpu+gpu) spin up and immediatelly spin down
• this loop is repeating indefitely
• if notebook is on battery, then there is like 1minute delay before the loop begins again, if it is on AC adaptor, the loop repeats immediately (like in video)
• this loop is exactly the same I experienced 2 years ago, but at that time I still had the warranty, under which I sent it to the repair center where they fixed it by, quoting: "Repaired by CMOS reset."
• one common sign, which could cause this loop is in my opinion some shady BIOS update from HP side, because 2 years ago, when the loop begins for the first time, I updated BIOS while the official HP drivers utility marked is as critical (or such), everything was fine for around 2 days, after that the loop started... Fast forward to present time, the same utility suggested again new BIOS (v1.52 I think) and almost exactly after 2 days the dreadfull loop begins again (btw, notebook is in mint condition, as I care about things I use for work, especially when my configuration was almost the highest possible, minus the DreamColor LCD.

So after all, I decided, based on the report from first repair, to reset CMOS by myself per instruction from HP site, I tried:

1. unplugged AC adaptor
2. removing everything internally connected to MB (internall battery, ssd/hdd drives, RAM sticks, RTC battery, expansion cards, WLAN card, keyboard, etc...)
3. drained the residual current by holding power button for 10/30/60sec...
4. reseating RTC battery after few minutes/few hours/day..., also bought new RTC battery, which I tried too
5.  reseating everything piece by piece (to detect probably faulty item)
6.  tried every suggested key combinations with power button (win + V, win + B, ESC+UP+DOWN), also tried USB BIOS recovery
7. tried to run without RTC battery
8. tried to run only on AC adaptor, or only on internall battery, or with AC + battery, tried two different original AC adaptors too, also with TB3 dock too

Every steps I made made zero difference, not a single different behavior, still the same loop.
From what I gathered via google-fu, it seems that the service center which made first CMOS reset repair, is not the same as I am trying per suggestion by HP.
The notebook has some kind of NVRAM which is not cleared by suggested steps, thus not fully wiping BIOS settings to default state, which I think is the problem. When the notebook had CMOS cleared by service center, my BIOS password was gone. But from what I learned, the suggested DIY steps wont clear the NVRAM, where the password is stored. So I think, that beside the password, there are more setting stored in that NVRAM, which are causing the loop - thats why all of my efforts are in vain. Also I totally think, that all of the notebook parts are fine, so I hope I wont hear some usuall BS : replace mainboard for 400Euro...

So my final quesiton for the HP officials/service - Can you please reveal how to fully reset CMOS, thus wiping BIOS to default state? I dont care about password, I know it. I just want the **bleep** thing to run again, and not to be ruined by, what I believe **extremely shady** practice by HP with BIOS updates, which will force user to buy unnecesary new mainboard.

Thanks in advance.

-M