This iPhone 6 has been liquid damaged and after we’ve cleaned the board and tried to turn it on we found out phone doesn’t boot properly and when we’ve restored it with iTunes we received error 4013 and phone got stuck on iTunes recovery mode.

In this case, we have to remove the nand ic chip and put it into the nand programmer and program it again to fix error 4013. After all, we’ve reballed the nand ic and installed it on the logic board and restored it by iTunes Completely and phone turned on without any issue.