a litle Car Computer Question

This may sound like a wierd question but, here..Do car computers/chips have some code of signal in them that is different in every car? Something that comes standard in most cars and can be made electronicaly trackable. Code,#,signal, you name it (NOT NON electro or detachables) if it differs in every car I want to hear about it.

I've searched the internet, but couldn't find much. If you have an answer to this question or know of a website that will answer my question please post. Thanks!

  The-One