Comment by nimbius | Hacker News Reader

Comment by nimbius | Hacker News Reader

as a professional diesel mechanic for a small chain of midwest shops, this "telematics" feature is on long-haul trucks as well as tractors (john deer is notorious for using it to send mail marketing about services.)

generally its not hard to disable.

- identify the telematics module in your car - pull the fuse (not always an option, sometimes this disables bluetooth)

- alternatively: identify the 1-2 SMC connectors on the telematics device. this is the LTE and low/alt channel for the cellular communications. disconnect these 1-2 connectors and connect the ports instead to a 50 ohm terminator. the vehicle will simply continue to collect data but never be able to send it anywhere. the system will assume it just cant find a tower.

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.

The Toyota community has been far down that road with the DCM module in the new gen cars and found that the car still managed to get updates out to Toyota even with 50 ohm terminating resistors in the antenna connectors: https://www.tacomaworld.com/threads/simpler-solution-for-dis... (see the posts by user "Disgruntled Scientist").

Unfortunately simply cutting power to the telematics module also disables the in-car microphone for handfree calling. Fully disabling telematics involves making a bypass harness that re-routes the microphone and speaker signals past the disabled DCM module.

Connecting to a dummy load is a pretty good idea I hadn't thought of (usually I just disconnect the cellular module).

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