No, an immobilizer is not an alarm system. It is an electronic device that is fitted in your car to make it impossible for thieves and intruders to drive your car away. You should understand that most thieves can disable an alarm system and render it useless within seconds, but immobilizers cannot be overridden. With an immobilizer, your car can only be stolen if it is towed away, and even then, the thieves will not be able to start it wherever they take it.