Circuit/System Description
WARNING: This page is about a different car, the 2017 Chevrolet Spark. However, it is still accessible from the selected car via links, so may be relevant.
The multi-band antenna is located on the roof of the vehicle. The radio antenna is enabled when the radio is turned on. The radio provides battery voltage to the antenna using the center conductor of the antenna coaxial cable. When a 12 V signal is seen on the center conductor of the antenna coax, both AM and FM signals are amplified.