If you're being extra paranoid, you'd need to spoof a cell tower. Spoofing a Wifi AP and monitoring traffic with Wireshark gets you network traffic, but you can't know if the vehicle sends certain information exclusively over the cell network, short of on-vehicle firmware and software analysis. Also, if you wanted to go with the Wifi approach, you need to force Wifi connectivity, which would probably mean going outside of cell tower coverage or unplugging the vehicle's cellular antenna, both of which may affect what the car transmits.