Security system how to put on

If the vehicle has a factory installed security system you need to have all the keys programmed to the vehicle removed from the vehicle's memory. Then program the keys you have to the vehicle. Doing that will prevent other keys from being used to start and steal the vehicle. A reputable locksmith or your local GM Dealer will be able to do this for you. If the vehicle doesn't have a factory installed security system, replace the ignition lock cylinder. That will prevent other keys from being used as well. You can buy a set of locks for the doors and ignition that are keyed alike. So the car can't be unlocked with an old key as well. Hope that helps! Jim