Will an iMac boot if EFI is bad or fried?

[Zataralos]

changed the EFI chip (firmware lock) on my iMac and now it won’t boot. Symptom is LED1 on, LED2 flashing every 5 seconds. The PS seems to be ok, I can measure 12V getting to the logic board. Power button does nothing. Before I start looking for shorts, etc, wondering if the new chip is either bad or fried during installation. It's a 2017 iMac 21.5 4K.

Any help would be appreciated?

[aqibi2000]

Put the old one back on and confirm

It’ll only take you 10 min to strip down and some hot air  for do the swap

Why would you start looking for “shorts” before doing the above?

[garrettm]

Couldn't you have used an in circuit programmer to save the old firmware and then flash the hacked firmware? I remember people doing this with PC motherboards to neuter the Intel Management Engine for v11.x firmware. Seems a little easier than unsoldering / soldering in a new chip.

https://wiki.gentoo.org/wiki/Sakaki%27s_EFI_Install_Guide/Disabling_the_Intel_Management_Engine

I've been building computers since middle school, and even when I flashed the wrong bios the motherboard would at least still turn on when the power switch was pressed. So you may have damaged something on the mainboard while swapping out chips. Electrostatic discharge kills. I inadvertently euthanized my old PC when I shocked the outer case... Turned out that Silverstone had designed the removable front panel to be electrically floating with the PWR_LED, HDD_LED, PWR_SWT, and RST_SWT running behind it. That shock then went to the closest conductor/s: the front panel wiring and fried the mobo. It was a very sad day for me and my wallet.

[aqibi2000]

Garrotte This is not how the HM65 and HM55 PCH architecture works

It has to pass RSMRST first to get the SIO to transition from the S5 state.

The word “boot” really isn’t the right term.
There are 5 power up stages