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Question PC boots for maximum 5 seconds - and only when CPU unplugged

Feb 6, 2020
Hi everyone, I know we’ve all seen a thousand threads just like this (and I’ve gone through as many steps from the troubleshooting checklist as I can), but none that I’ve seen match my situation so here we go...

I recently bought a new motherboard (Gigabyte B365M DS3H) and am trying to use my old processor (Pentium G4560) until my new processor is delivered.

I also installed a new Thermaltake cpu cooler.

When I turn the pc on, all the fans spin, I get a few lights (one orange strip near the back back of the motherboard (just decoration I think?), a blue led from the front panel / power button (my case is a Thermaltake V21), and one beep from the mobo, which apparently means success - all at once for about a half second, then everything shuts off.
I’ve figured out that if I u plug my 8-pin CPU cord from the motherboard, it will boot for about 5 seconds before shutting off.

I’m assuming it’s my CPU that’s faulty, but I’d really like to figure it out before my new processor is here as I am already getting frustrated (there’s more backstory than necessary).

BTW it is already breadboarded and I cannot test my PSU (which has never given me a problem) because I have no other pc and there is no “green wire” to short, they’re all black. Additionally I’ve tried moving my RAM to every other slot with no difference, and my GPU isn’t installed at the moment. cmos has been cleared more than once.

please help, cheers!