How to ensure my car works properly after changing ECU

Question

Brain box was stolen; I have replaced it but it's not working properly. Car fails to start after key is turned in the ignition. Security light remains on ( the immobiliser system )

Answer 1

Anytime the ECM is replaced the ECM need to be reprogramed for key code registration, there are 2 ways to do this with the scan tool or the brake pedal and accleration pedal method. use this method if you do not have the factory grade protocal scan tool your master key will be the one you would use all the time