Comment by m463

I tried this with a wifi setup on a car charger. I connected a 50-ohm dummy load in place of the antenna using the mmcx connector.

It didn't work - there was an on-module antenna that it switched to. Might not have worked as well, but it did work and the wifi access point still showed up.

On the other hand, some cars have a self-contained telematics module like you said and you can just unpower the whole thing.

I remember looking at a ford owners manual for a 2019. The fusebox section had a fuse with description "Telematics control unit - modem." I assume you can just pull that fuse.