Holy wirings, Batman! Again!

Just spent better part of three hours removing the engine wiring harness. I did bleed the oil and the coolant as well, but that didn't take too long. The ECU and old 12 V battery tray came out as well. If you turn they key now there's a 30 second beep and a Key light flashing. Probably the electric engine immobiliser is not happy for some reason or another. There might be a way to reset it though.