Anger over ICE connections and privacy violations is fueling the sabotage. PLUS: 10,000 drivers call on Uber to repay stolen wages, a man is arrested at a public hearing about a data center and more.
A city near me has installed a device that tracks vehicles based on their tpms (Tire Pressure Monitoring System) sensors.
All cars after 2008 in the US have TPMS. Inside the tire, integrated with the vale stem, are little pressure sensors with a radio that broadcasts on the 315Mhz band. Each one uses a slightly different frequency so that your vehicle can tell which of the four tires is low.
So each vehicle in the US made after 2008 has four unique radio signals being broadcast from it, and now there are police departments with equipment that can track those signals, and can assign each car a signature based on the frequencies the sensors are broadcasting on.
Well, from my knowledge, the person you replied to is inaccurate. All tires will transmit at the same frequency. But every X seconds, when each tire transmits its data, it transmits an ID unique to its transmitter with it.
Every X seconds is pretty generous. My Subaru only seems to poll the sensors every few minutes, and only when the wheel speed is above 35 MPH or so, at least via what I’ve observed with my diagnostic tool. The sensors are battery powered and I suspect the low refresh rate is a deliberate gambit to conserve battery life.
You are correct on the ID point, though. They can contain up to 16 hexidecimal digits as far as I’ve seen, and while there doesn’t seem to be any mechanism for truly enforcing uniqueness the chances of an ID collision are so low that you may as well consider it impossible. Some aftermarket sensors can be wirelessly reprogrammed with an arbitrary ID, though, which may be of marginal utility for the truly paranoid. (My diagnostic tool can do this, too. The intended use case is cloning the ID from an OEM sensor for a car whose TPMS relearn procedure is more trouble than it’s worth.)
Regardless of your vehicle’s polling frequency, most sensors can be woken up any time by a specific radio pulse, which my diagnostic tool can also do, and the range is surprisingly long. Just my car’s own BMS where the receiver is (above the rear left wheel well) can pick up the sensors in my snow tire rims even when said rims are sitting in their storage rack inside my garage, about three car lengths away.
If my memory serves well, it is configurable. I say X seconds because it can be 5, 10, 30, but of course also 60, 120… This is my programmer brain talking :)
Thanks for the comment though. Much more complete than mine.
A city near me has installed a device that tracks vehicles based on their tpms (Tire Pressure Monitoring System) sensors.
All cars after 2008 in the US have TPMS. Inside the tire, integrated with the vale stem, are little pressure sensors with a radio that broadcasts on the 315Mhz band. Each one uses a slightly different frequency so that your vehicle can tell which of the four tires is low.
So each vehicle in the US made after 2008 has four unique radio signals being broadcast from it, and now there are police departments with equipment that can track those signals, and can assign each car a signature based on the frequencies the sensors are broadcasting on.
That’s alarming, but how much can these really vary? I’d be surprised if a lot of vehicles weren’t the same.
Well, from my knowledge, the person you replied to is inaccurate. All tires will transmit at the same frequency. But every X seconds, when each tire transmits its data, it transmits an ID unique to its transmitter with it.
Every X seconds is pretty generous. My Subaru only seems to poll the sensors every few minutes, and only when the wheel speed is above 35 MPH or so, at least via what I’ve observed with my diagnostic tool. The sensors are battery powered and I suspect the low refresh rate is a deliberate gambit to conserve battery life.
You are correct on the ID point, though. They can contain up to 16 hexidecimal digits as far as I’ve seen, and while there doesn’t seem to be any mechanism for truly enforcing uniqueness the chances of an ID collision are so low that you may as well consider it impossible. Some aftermarket sensors can be wirelessly reprogrammed with an arbitrary ID, though, which may be of marginal utility for the truly paranoid. (My diagnostic tool can do this, too. The intended use case is cloning the ID from an OEM sensor for a car whose TPMS relearn procedure is more trouble than it’s worth.)
Regardless of your vehicle’s polling frequency, most sensors can be woken up any time by a specific radio pulse, which my diagnostic tool can also do, and the range is surprisingly long. Just my car’s own BMS where the receiver is (above the rear left wheel well) can pick up the sensors in my snow tire rims even when said rims are sitting in their storage rack inside my garage, about three car lengths away.
If my memory serves well, it is configurable. I say X seconds because it can be 5, 10, 30, but of course also 60, 120… This is my programmer brain talking :)
Thanks for the comment though. Much more complete than mine.