Problem with the MacBook Pro 13 "A1278 (EMC 2419)

Hello friends, help you if possible!
I'm trying to unlock a MacBook Pro 13 "A1278 (EMC 2419) has modified the ROM erasing the $ SVS and does not give me the option of pressing" Option "to enter to choose the partition to install the new system, only goes toward the apple and asks for the PIN code of 4 digits!

What could be happening?

Hello friends, I ended up finding one here in the forum repository, which ended up giving it right!
MacBook unlocked and updated!
Hug to everyone.

Just for anybody else who stumbles onto this thread:

The iCloud lock and the EFI lock are two separate entities, both stored in the EFI chip.

Modifying your FW dump removes the EFI lock, but not the iCloud lock.

After removing the EFI lock, you must clear the remainder of the NVRAM to remove the iCloud lock. This is done either from single user mode typing "nvram -c" or by booting the Mac holding the CMD+OPT+P+R keys until it reboots.

That being said, do not load the existing OS X installation, always erase and reinstall OS X from DVD or USB media.