MacBook Pro (Retina, 13-inch, Early 2015) 2 Minute Pre boot Delay

MacBook Pro (Retina, 13-inch, Early 2015), has Latest OS, Big Sur, 11.5.2 (20G95), and System Firmware Version: 427.140.8.0.0.

Whenever I try to boot it normally, into recovery mode, Safe mode there is a delay of 2 minutes between pressing the power button and the startup chime and apple logo.

I have tried SMC reset, NVRAM Reset, Setting SSD as startup disk and many more commonly suggested fixes.

I think based on my research, There are some pre-boot tests it performs before the startup chime happens and the Apple logo is displayed, So it might be taking too long to finish those tests. All the parts are original.

I have run apple diagnostics and used various other tools like Disk Utility, Etrecheck, and many more but no issues were found. Further, the MacBook runs fully optimally when it boots up, with No issues whatsoever.

I opened the MacBook a few days ago to clean the fan, that's when the issue started. I have tried removing SDD, Fan, IO Board, Display cable, Battery, and starting the mac but none has managed to kill that 2-minute boot delay before startup chime.

Does anybody have an idea, which issue it might be, and how to fix it?

Regards