The easiest way to do this is usually to unplug the antenna and replace it with an RF terminator. The vehicle will simply think it is always out of range of cellular service. Unfortunately most modern vehicles require a lot of finagling to disable the telematics control module itself without causing error messages.

It would be nice if some regulator would mandate an "easy-off" function for vehicle telematics - some kind of simple procedure which would remove a telematics module from the installation list and allow the module to be unplugged without triggering fault detection. This is possible on some cars using dealership tools to re-train (sometimes called "code") the configuration blobs in each control module to omit telematics, but it's not standardized and usually too difficult for a consumer to manage.

Unfortunately, the regulators (NHTSA) are inches away from mandating cellular be added to cars (if they haven't already pulled that lever).

they haven't yet, but the technology is there and is mandatory in large parts of the world

https://en.wikipedia.org/wiki/ECall

https://www.atic-ts.com/vehicle-accident-emergency-call-glob...

https://en.wikipedia.org/wiki/Enhanced_9-1-1

For most manufacturers, you can purchase access to the technical documentation for a short period. I paid Toyota $20 for 48 hours of access and got PDFs of the official instructions for how to remove the 4G module.

How do you find the contact for this?

Also, how hard was it to find the section for removing the module, and how hard was removing the module in your case?

I have a Subaru, but still curious about yours.

Could potentially Faraday cage it if you can find the exact spot it's at.

Careful with that or it might just eat up your battery trying to contact cellular towers at maximum power with a short retry interval.

The module should go to sleep, and the battery management should also load-shed it if it detects the battery draining. I suspect this is probably not implemented correctly on some cars (because what is), but it's definitely something that's tested for regularly (since cars can be expected to be taken camping, off the grid, or even just purchased by owners who live outside of cellular coverage).

> The module should go to sleep

lol tell Subaru owners about this. There are tons of them complaining of batteries going dead the last few years, just from sitting a few days in the driveway, while the always-on cellular is at edge of range, hunting. Subaru's solution to this has been to in some cases pay for a bigger battery for those customers.

Maybe an other way around solution? Is is possible to build some kind of dummy cell tower that supersedes real ones?

Good luck with that. This is illegal (in europe)

What make and model?