My 2005 Civic has a bad ECU, it throws random P0600--P0606 codes but runs great, all wiring is good. I would not even bother changing the ECU if I knew it would not die and strand me. I got a junkyard ECU from a 2004 Civic auto, and took the car to a Honda dealer to have the new ECU flashed, but they said the immobilizer would not flash. They did not know why, so they said I could get another ECU and come back and they would try again at no cost since I already paid them. The second junkyard ECU from a 2005 Civic auto would not flash either. Is there a reason this would happen? I wonder if they even tried to flash it. No one I talked to has ever heard of this and no one seems to know what causes this. Please help, I do not know what to do. Thanks!