5 ms·

There's still a fuse for the DCM even in this car but: - It has an internal battery and will keep running for quite a while after pulling the fuse. This is a s

There's still a fuse for the DCM even in this car but: - 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

brewdad 5mo ago
GPS is receive only. If you've disabled the ability to send telemetry, there should be no reason to be concerned about the GPS antenna.
- fc417fc802 5mo ago
  If it keeps collecting telemetry it could upload it later if it ever gets the chance. Better it isn't collected in the first place.
  - drnick1 5mo ago
    Good point, but in practice I think the only way onboard data could be exfiltrated is by a dealer while the car is being serviced. If you DIY or hire an independent mechanic, this seems unlikely.
    - throwway120385 5mo ago
      Or by the FBI, NSA, CIA, DHS, or some other interested entity.
      - willis936 5mo ago
        If a TLA is interested in you then you don't need to worry about a data log in your car.
        Arch-TK 5mo ago
        I find comfort in thinking that, if a TLA is interested in me, they have to work a little bit harder.
        willis936 5mo ago
        They don't. They have all internet traffic dragnetted and satellite imaging and radar far beyond what is publicly disclosed. They don't need to check in with some low res crap that insurance companies use to nickel and dime you. If you're trying to escape surveillance and control from TLAs then you better start your moon base plans soon.
      - mothballed 5mo ago
        The kind of organized crime that those people should be focused on are also resistant to this kind of tracking. The cartels and gangs just use burner cars that they dump, possibly with the keys and title still in it. Good luck doing much with the log but you've got the log and even the entire car to try and gather all the evidence you want. This tracking is mainly for hemming up small fry and productive citizens.
  - willis936 5mo ago
    That also means it isn't passed to your phone via android auto / carplay. Phone GPS is much worse than car GPS for road navigation. It's basically unusable.
    - Arch-TK 5mo ago
      I've successfully used it in my 2006 Ford Fiesta for about 10 years now... The reliability is way better than GitHub's uptime. Better even than my car's uptime. You must work in telco. 99.9999% or it's unusable :P
      - willis936 5mo ago
        My SO immediately sniffed out when the GPS antenna was unplugged from a car with carplay. Unacceptably low spouse approval factor.
  - tmerc 5mo ago
    Storage space is limited. There's a black box for accidents that keeps a rolling window of data. That's not the dcm. Outside of that, how much telemetry can you store? What's the retention when there's no cellular connection? And importantly, where is it stored? My guess is that the dcm, having a battery back up and a cellular connection, is also the telemetry store. No evidence other than it's the cheapest and most reliable way to do it. At least for Subaru, the dcm also connects to all antenna so removing it disconnects gps antenna. For other cars, I'd still expect removing the dcm to be good enough for 95% of people given the current expectation from car companies that no one would want to remove the dcm.
    - fc417fc802 5mo ago
      That's an interesting point but consider that bandwidth is also limited when we're talking about an always on system that's in every vehicle sold. And until recently storage was remarkably cheap. If you log 32 bytes once per second that's only 962 MiB per year uncompressed. But 32 bytes is a lot (or depending on what you're logging not very much), once per second is almost certainly more frequent than necessary, and almost all vehicles spend the vast majority of their time turned off. For example logging RPM every 100 ms, 8 bits gets you reasonable but not perfect accuracy and you're looking at 300 MiB per year of continuous operation. It's just not much of a storage requirement for quite detailed telemetry.
      - aaronbeekay 5mo ago
        Yah, but automakers are very cost-sensitive, and flash memory/NVM is one of the easiest places to penny-pinch. I get crap about 2kB payloads.
- arkadiyt 5mo ago
  This is addressed in the blog :)
- kotaKat 5mo ago
  My Ford ~(2018 era SYNC system) has GPS and Bluetooth but no cellular modem. It still technically is used for telemetry... but only when you get into a wreck. It'll ping the onboard GPS at that time for coordinates, then place a voice call over your paired cellphone to 911 with TTS coordinates and information about the wreck. "Attention. A side crash with rollover has occured in a Ford vehicle. Multiple impacts detected. The maximum speed change was 38 miles per hour. Airbags deployed. Detected ONE seatbelt fastened. Press 1 at any time for location information, or press 0 at any time to speak with vehicle occupants."

brewdad 5mo ago

GPS is receive only. If you've disabled the ability to send telemetry, there should be no reason to be concerned about the GPS antenna.

fc417fc802 5mo ago
If it keeps collecting telemetry it could upload it later if it ever gets the chance. Better it isn't collected in the first place.
- drnick1 5mo ago
  Good point, but in practice I think the only way onboard data could be exfiltrated is by a dealer while the car is being serviced. If you DIY or hire an independent mechanic, this seems unlikely.
  - throwway120385 5mo ago
    Or by the FBI, NSA, CIA, DHS, or some other interested entity.
    - willis936 5mo ago
      If a TLA is interested in you then you don't need to worry about a data log in your car.
      - Arch-TK 5mo ago
        I find comfort in thinking that, if a TLA is interested in me, they have to work a little bit harder.
        willis936 5mo ago
        They don't. They have all internet traffic dragnetted and satellite imaging and radar far beyond what is publicly disclosed. They don't need to check in with some low res crap that insurance companies use to nickel and dime you. If you're trying to escape surveillance and control from TLAs then you better start your moon base plans soon.
    - mothballed 5mo ago
      The kind of organized crime that those people should be focused on are also resistant to this kind of tracking. The cartels and gangs just use burner cars that they dump, possibly with the keys and title still in it. Good luck doing much with the log but you've got the log and even the entire car to try and gather all the evidence you want. This tracking is mainly for hemming up small fry and productive citizens.
- willis936 5mo ago
  That also means it isn't passed to your phone via android auto / carplay. Phone GPS is much worse than car GPS for road navigation. It's basically unusable.
  - Arch-TK 5mo ago
    I've successfully used it in my 2006 Ford Fiesta for about 10 years now... The reliability is way better than GitHub's uptime. Better even than my car's uptime. You must work in telco. 99.9999% or it's unusable :P
    - willis936 5mo ago
      My SO immediately sniffed out when the GPS antenna was unplugged from a car with carplay. Unacceptably low spouse approval factor.
- tmerc 5mo ago
  Storage space is limited. There's a black box for accidents that keeps a rolling window of data. That's not the dcm. Outside of that, how much telemetry can you store? What's the retention when there's no cellular connection? And importantly, where is it stored? My guess is that the dcm, having a battery back up and a cellular connection, is also the telemetry store. No evidence other than it's the cheapest and most reliable way to do it. At least for Subaru, the dcm also connects to all antenna so removing it disconnects gps antenna. For other cars, I'd still expect removing the dcm to be good enough for 95% of people given the current expectation from car companies that no one would want to remove the dcm.
  - fc417fc802 5mo ago
    That's an interesting point but consider that bandwidth is also limited when we're talking about an always on system that's in every vehicle sold. And until recently storage was remarkably cheap. If you log 32 bytes once per second that's only 962 MiB per year uncompressed. But 32 bytes is a lot (or depending on what you're logging not very much), once per second is almost certainly more frequent than necessary, and almost all vehicles spend the vast majority of their time turned off. For example logging RPM every 100 ms, 8 bits gets you reasonable but not perfect accuracy and you're looking at 300 MiB per year of continuous operation. It's just not much of a storage requirement for quite detailed telemetry.
    - aaronbeekay 5mo ago
      Yah, but automakers are very cost-sensitive, and flash memory/NVM is one of the easiest places to penny-pinch. I get crap about 2kB payloads.
arkadiyt 5mo ago
This is addressed in the blog :)
kotaKat 5mo ago
My Ford ~(2018 era SYNC system) has GPS and Bluetooth but no cellular modem. It still technically is used for telemetry... but only when you get into a wreck. It'll ping the onboard GPS at that time for coordinates, then place a voice call over your paired cellphone to 911 with TTS coordinates and information about the wreck. "Attention. A side crash with rollover has occured in a Ford vehicle. Multiple impacts detected. The maximum speed change was 38 miles per hour. Airbags deployed. Detected ONE seatbelt fastened. Press 1 at any time for location information, or press 0 at any time to speak with vehicle occupants."