I have a new-ish car that doesn't have 3.5mm aux input. I don't want to use bluetooth. I want to use Google Play from my phone to my car's audio system but it looks like the only real inputs are bluetooth and hdmi. It has USB, but I'm pretty sure that's just for playing data from thumb drives.
It seems to be a common complaint with that year and model.
Adding an amp with an input jack that disconnects the head & allows you to play the phone using it as the volume control should work but may not be any cheaper than replacing the head.
At the risk of sounding like Mr. obvious, the car's manual should say exactly what you can do.
The manual doesn't mention anything about a 3.5mm input because the car isn't equipped with one. I was hoping there was some workaround using some kind of an adapter. 3.5mm to bluetooth doesn't count because I don't want to use bluetooth. HDMI is locked out when driving, which pretty much leaves USB as the only possible input, but I think the only use for the USB is for a thumb drive containing just files.