Unbrick Any PS3 - Copied From Another Source -
So, I loaded up retail firmware 3.15 on to a usb stick along with the Diag2.self file from Folder 1. as i figured out that it must be some incompatiblity with the fimware update.
Put the PS3 into service mode (put the jig/dongle in the far right port).
NOTE: The screen will stay black at all times even if you try to load up to service mode.You’ll just have to do it “blind” so dont panic. You will be able to tell that it went into service mode by the dongle going green, or whatever color yours goes. it will go to standby. Don’t worry as thats a good sign.
Now take out the dongle and place it in the same port you pulled the jig out of. Turn the PS3 back on, and let the dongle work its magic. 4 or so minutes later, the ps3 will go to standby.
Once this is done, remove te USB stick, format it and place the Diag2.self file from FOLDER 2 Turn the PS3 Back on and the USB will blink then the PS3 will go into standby again.
One more thing, NEVER EVER UPDATE IN SERVICE MODE!! YOU WILL GET A RED SCREEN OF EPIC FAIL!!. (as quoted by someone on IRC.) you should only downgrade or reinistall the same firmware you have on your PS3.
The reason why i didnt mention it before is because i hadn't slept for 2 days, so forgive my tiredness.
Turn on the PS3 and you should have a fully working PS3 again.