It let me disable telematics, and Kia support confirmed that my car was flagged as a "Massachusetts variant" even though it wasn't purchased in MA.

How far do you live from Massachusetts, and how do your feel about driving vacations?

On newer vdubs there’s both a “location services” and a “offline mode” toggle in the infotainment, though this only turns the infotainment SIM off. Obviously this also disables remotely controlling the car using the app.

And the secondary eCall SIM cannot be disabled - not without triggering a fault code and a tell-tale. Since eCall is considered a safety-critical system it has self-monitoring and must work for the vehicle to pass inspection. It even has its own separate power supply. This is true for any vehicle (type) newer than ~2018 in the EU. This probably makes tracking the rough location of any eCall-equipped vehicle quite easy, if you have signaling-level access to the cell network – exactly like in all those SS7 exploits.

edit: turns out they thought about that and eCall modules aren’t supposed to constantly stay connected to a cellular network (dormant mode). Instead they only log onto the cellular network when needed. Difficult to verify as a consumer though.

I would be very concerned that the flag just continues to submit your data but with a "telematics disabled" bit set on it. This is absolutely how location privacy is implemented in some devices. Moreover, even if it is effective it could be remotely reset including accidentally as part of an update.

Better than not setting it, I suppose! :)

- It has an internal battery and will keep running for quite a while after pulling the fuse. This is a safety feature in case you get in a crash that disconnects the 12V battery

- It will break your in-car microphone as discussed. Repairing that requires opening up the dash

- That won't do anything for disconnecting the GPS antenna