My question is...where and how many sensors are in our trucks for CA?

It's weird...when I leave a fob in the center console and take one with me, I can lock the doors. The driver's side isn't supposed to lock if it detects a key is inside the vehicle. The keyfob inside's battery is fine so it's not like it's just a dead battery and the truck doesn't detect it.

Do we have a few sensors inside the truck in order to triangulate the position of the keyfobs? Or is it just one that uses some sort of radio measuring to detect and pinpoint where the keyfob(s) are?