Cell modems are pretty amazing. One time I wanted to simulate losing reception on one, so I removed the antenna. It still worked, so I added a 50 ohm termination. It still worked. I finally got it to disconnect by putting it all inside an anti-static bag.

Are they? I remember disconneting the antennas of some of my devices for repair purposes and getting no reception at all (not even for emergency calls).

Maybe things changed in the last few years

Many radios have more margin on the signal once "connected". I vaguely recall that cell modems in particular need to do an initial registration with the network. That registration is probably at a fairly ancient modulation, without the benefit of the cell tower knowing where the modem is to beam form to it. It seems like that could account for 10's of dB of difference.

There is a waterproof "fuse box" in every car, similar in function to breaker box in a house, on front firewall(even for rear-engined cars!). "Pull a fuse" means removing a fuse for offending subsystem(ECU) to simply disable it, such as ABS, as clean as `apt uninstall sl` would go. What the guy above you is saying is you should be able to turn off "security feature" altogether and the car should revert to an insecure car.

But considering that Teslas are infamous for authenticating every start/stop of individual cars between the key and the infotainment computer and a datacenter in California...

I can't tell if your last sentence is sarcastic? But a Tesla doesn't call home to authenticate the kefob. Otherwise you'd never able to start the car outside of cellular reception.

Of course, but I was just speaking generally, I'm not sure how teslas are laid out and the accessibility of any given component.

Let's say that with enough effort you can probably reach it. But if to do that, you have to disassemble half of the car, then it's possibly not convenient to do so :D

https://www.auto-manual.com/tesla/tesla-model-3/

The wiring diagram you've linked and a few well aimed drill bits should do the trick.

Otherwise a big enough faraday cage works too. It's just not that convenient :)

I wonder how well this would work. Wouldn't the Faraday cage need to be tuned to the wavelength of the cellular radio?

Someone elsewhere suggested putting the car in a cargo container, but I don't think that works either. I was on a large ferry recently, my phone worked below deck several inclusive distance units away from the coast.