Centralized closure wrench failure

Greetings to all. It is my first entry into the forum and for what I see is very interesting. I would like to know if someone has an idea where the transponder or receiver of the centralized key is located. I have only opened the car directly with the key. I have put a new battery in command, I have checked all the fuses, etc. In my opinion as a simple fan, or it is the module that goes inside the key or antenna of the receiver that goes in the car. In some models it goes under the driver's seat but I don't see it in this. It is a Hyundai Terracan 2.9 CRDI of 2005. Thank you anticipated who can clarify the doubt.