Passive Key
WARNING: This page is about a different car, the 2016 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.
The Passive key incorporates both the PATS and the RKE transmitter functions in a single device. The Passive key must be located inside the vehicle for engine starting. When the Passive key is activated it sends out a frequency signal that is received by the TPM. The Passive key also contains a key blade that is used to enter the vehicle as a backup.