External RF Antenna
WARNING: This page is about a different car, the 2010 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.
The external RF antenna is located in the back glass, just under the rear defrost grid. There is a coax antenna that connects the antenna in the back glass to the RCDLR. This antenna is responsible for receiving the RF communication from the TPM senders and the keyless entry transmitters (for both active and passive functions).