Question Pc won't boot, CPU led on mobo, instantly turns off and boot loops

[Polanker]

Hi all,

I built this system around 8 months ago, no issues until now.
I use it daily, and was using it this morning. I walked away for 30 mins, came back and it was boot looping.
It turns on for less than a second, turns off (with the psu click sound) and loops until I turn the psu switch off.

What I've tried:
Clearing cmos by removing battery for 15mins+ as well as jumping the clear pins.
Disconnecting all peripherals
Testing every combination of ram slots, as well as removing ram completely.
Disconnecting and reconnecting gpu
Reseating CPU with fresh thermal paste
Unplugging and replugging all cables at mobo end and psu end
Disconnecting all hdd's, removing nvme boot drive
Cleaning all case dust/fan dust
Confirming CPU fans are spinning on boot
Testing new power cable
Connecting hdmi to igpu and disconnecting gpu

Every single one of these tests have had the exact same result.

Parts:
12900k
msi z690-a pro wifi ddr4
Corsair lpx 3200 c16 2x32gb
Evga 3080ti xc3
Corsair hx1000
Samsung 980 pro boot drive
Noctua d15

Don't have a spare mobo/psu or CPU to test individual components.

Any help is greatly greatly appreciated.

 

[Lutfij]

Welcome to the forums, newcomer!

https://download.msi.com/archive/mnu_exe/mb/PROZ690-AWIFIDDR4_PROZ690-ADDR4100x150.pdf
Your motherboard has a feature to flash the BIOS without the need to POST(and get into the BIOS or OS GUI), turn to page 30 in your motherboard manual, follow instructions listed under Updating BIOS with Flash BIOS Button .

Once you've verified that the BIOS was flashed successfully, clear the CMOS. You do this by disconnecting from the wall and display, then remove the CMOS battery, press and hold down the power button for 30 seconds and then replace the CMOS battery after 30 mins.

If that doesn't help, try and relieve some pressure from the mounting of the cooler and see if that allows you to POST/get to OS GUI.

How old is the PSU in your build?

 

[Polanker]

Welcome to the forums, newcomer!

https://download.msi.com/archive/mnu_exe/mb/PROZ690-AWIFIDDR4_PROZ690-ADDR4100x150.pdf
Your motherboard has a feature to flash the BIOS without the need to POST(and get into the BIOS or OS GUI), turn to page 30 in your motherboard manual, follow instructions listed under Updating BIOS with Flash BIOS Button .

Once you've verified that the BIOS was flashed successfully, clear the CMOS. You do this by disconnecting from the wall and display, then remove the CMOS battery, press and hold down the power button for 30 seconds and then replace the CMOS battery after 30 mins.

If that doesn't help, try and relieve some pressure from the mounting of the cooler and see if that allows you to POST/get to OS GUI.

How old is the PSU in your build?

Hi Lutfij,

Thanks for the welcome and thanks for the suggestions.

I will try to flash the bios tomorrow, just confirming why would I clear the cmos after flashing? I thought clearing cmos would reset the bios.

PSU is the same age, around 8 months.

Also confirming I checked CPU and mobo, could not find any bent pins, which wouldn't make sense anyway as this happened suddenly, haven't touched the CPU / cooler for months

 

[Lutfij]

Sometimes former BIOS version settings tend to linger in spite of a BIOS update. You might want to do a search across the forums, to learn that a clear CMOS after a BIOS flash did wonders.

 

[Polanker]

Sometimes former BIOS version settings tend to linger in spite of a BIOS update. You might want to do a search across the forums, to learn that a clear CMOS after a BIOS flash did wonders.

Thanks, I'll definitely try tomorrow. You said after I confirm the flash was successful, how can I confirm?

 

[Lutfij]

Did you find the page in the motherboard manual as I've outlined?

 

[Polanker]

Did you find the page in the motherboard manual as I've outlined?

Hi, yep sorry I got the info from the manual.

Unfortunately, I flashed the bios successfully and followed all your steps including removing cmos and powering down, but after adding the CPU and ram back its still doing the same thing.

Whats the most likely part to suddenly fry? I guess at this point it's most likely CPU or mobo right?

 

[Lutfij]

I wouldn't say fry...also if you're asking me to point a finger at any one component, I can't. Troubleshooting is a process of elimination, meaning you go through a checklist, until you're left with the logical conclusion. in your instance, if you want to pin this to the motherboard, drop your components onto a known working motherboard and see if the issue persists. If you want to pin the fault to the PSU, you source a unit that can power your entire rig. If the donor PSU powers the build without a hitch then the culprit was the PSU all along.