Q: question

The security system warning light should not illuminate once the vehicle is started and you are driving. If the light does illuminate, that means there is a malfunction in the security system. Obviously, if this problem started immediately after you changed the ignition switch and ECU on the car, it is probably a software related issue (in the ECU and/or in the receiver in the ignition switch if it is not properly programmed to the key) although, of course, there is always the possibility that what is occurring is just coincidental to the switch/ECU replacement and there really is a "new" problem in the immobilizer system and software. There are protocols in the Factory Service Manual to diagnose this and so you can request a warning light -immobilizer diagnostic and a mechanic will resolve this for you. In the course of that, the Mechanic will make sure the keys are programmed to the receiver and he or she might suggest re-flashing your ECU to the most current software version. If you request the warning light diagnostic the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.