He mentions cloning sensor ids, and indeed some sensors can be programmed to match an existing sensor. This comes in very handy if you have a set of winter tires. You can have multiple sets of tires that have a common set of sensor ids allowing you to swap sets in and out without having to reprogram the tpms.

Oh, that's smart. I just reprogram when I swap.

do you need to store them away from the vehicle when you park? i could imagine parking a car next to your stacked up winter tires in a garage would cause issues

I thought that might be an issue as well, but it hasn’t been. They’re stored about 15 feet away from the car.

The article also mentions this, many (most?) TPMS sensors to to sleep and wake up on movement. So as long as the other set of wheels isn't moving it should probably be fine.

TIL TPMS works over RF. The blog mentions that it's at a super low power, and not that I'd ever want this, but I can't help but wonder if it's possible to set up well-placed sensors at a fixed position on a road to capture IDs going by -- effectively tracking vehicles themselves.

Yes, it’s possible. https://m.youtube.com/watch?v=TDYoo7TGNcw&t=7m45s

To elaborate on the range of these things that others have mentioned, I too am seeing people's sensors from fairly far away.

I've got an RTL-SDR running rtl_433 on an RPi sitting in my living room, and I regularly see TPMS sensors from at least 6 different vehicles. The sensors identify as Renault, Schrader, Abarth 124 Spider, Schrader-EG53MA4, Citroen, and Ford.

For the Schrader ones I see enough different IDs that I think I'm seeing more than one car, so I'm probably seeing a few more than 6 different vehicles.

The antenna, which is just the little few inch thing long that came with the RTL-SDR, is about 85 feet from the street in front of my house, 60 feet from a dead end gravel road that runs by the side of my house, 113 feet and 116 feet from where my nearest two neighbors park, and 165 feet from where each of the next two nearest neighbors park.

The Citreon pressure is around 125 kPa, which is about half of what nearly everything else, so I'm curious what kind of vehicle that one is.

I'm the author of this post. I don't know why I had so much trouble picking up my own sensors. I agree, I've seen a lot of people say they can pick them up from pretty far away too. I'm still not sure about my antenna situation, but I just picked up a couple of Citroen sensors from a car driving by (~75 ft away) and they reported 130 and 131 kPa. I also saw one that was reporting 123 kPa during one of my drives while troubleshooting. Although my own "Citroen" sensors are definitely reporting the correct pressures, I'm thinking maybe there's another model that reports half of the actual pressure or something.

I'm also curious why they report a manufacturer of "Citroen". Isn't that a French automobile manufacturer? I wonder if someone originally observed this protocol on a Citroen car, but it's really just one of the main protocols used by the big TPMS sensor manufacturers like Schrader. I really doubt the sensors on my Dodge Ram are made by Citroen...

Both Dodge and Citröen are owned by Stellantis, so they're probably sharing some code or a supplier between the two brands.

FCA (Dodge) and PSA (Citroen) merger was started in 2019 so it's after the vehicle (2009) was sold.

I'm not too sure about the accuracy of the sensor IDs. I've supposedly seen several abarth spiders pass by my house but I've never actually seen one in person around me, they're not common near me.

I looked into this a couple years ago and a company had a patent for using TPMS tracking for traffic counts (instead of putting down those pneumatic tubes).

However, I seem to remember that new cars have been implementing something different so less and less cars will have this.

Yes, some cars use the abs sensors to detect rotation differences and estimate a low tire pressure scenario.

I was told by two different tire places that my wife's car (2015 CX-5) uses the ABS sensors to detect if one wheel is spinning differently than the others. A flat tire rotates faster than one full of air because it's smaller.

I had the warning light come on twice recently: once, I pulled over to the shoulder when an ambulance was approaching. As I accelerated to get back on the highway, the warning light came on. I thought I'd run over a piece of glass or something. Using the gauge showed nothing wrong. Reset the TPMS.

Later, we were starting on a 30-mile drive down a gravel road in Eastern Oregon. The TPMS light came on. I took a deep breath, kept driving and after we reached our destination, I reset the TPMS and it hasn't come on since.

My conclusion is that I accelerated too quickly on the shoulder and some gravel or debris made a wheel spin faster. The second time, there was presumably more gravel on one side of the car and again one of the wheels spun faster.

My wife's car is 2WD. I wonder if either would have happened in an AWD.

Nah, it's probably not slight wheelspin because that would be a normal case that's handled by traction control. It wouldn't make sense for the system to both control wheelspin with traction control AND report it as a low tire pressure condition. Presumably the TPMS alert would be triggered by a longer term rotational difference. It happens for all kinds of reasons (eg, going into colder temps).

I have a CX-5 2016, and done things like overheated the transmission in loose sand. Never had the TPMS come on from wheel slippage.

My car uses ABS for it and the light goes out after something like 10 seconds of non detection above 30 mph.

You likely have an ABS sensor issue - the wheel-speed sensor systems don't get triggered that quickly.

Newer Teslas are using Bluetooth Low Energy. I suspect that some other manufacturers might do something similar.

Yeah, you absolutely can - speaking from experience.

Of course. Bruce Schneier figured this out in 2008:

https://www.schneier.com/blog/archives/2008/04/tracking_vehi...

I can capture the TPMS data from my neighbor's vehicles from inside my house, with a barely-optimized antenna. It's not that low power.

Similarly, I am almost certain my car catches the sensors in the summer tires in the garage while I have my winter tires installed.

My winter tires don't have sensors, and it takes many KMs of driving before I get the sensor failure chime.

The same process repeats every morning.

This is definitely true for me. I take my car to the track, and my spare wheel/tire combos are stacked right next to where I park the car. When I take short trips around my town with my track wheels on, the TPMS light never illuminates. But about 30 minutes into my drive to the track, it comes on. It turns off again after I park in the garage again.

The sensors should stay off at rest though (There's acceleration sensors in the that activate them above a certain rpm value)

Many sensors will transmit once an hour (or some other long interval) to let the mothership know they're still alive. Or to warn you of a flat before you've left your house.

Don't license plates work just as well for tracking? And if it's the person and not the vehicle, phone tracking is more accurate.

RF tracking would be better if you don't have access to a location with line-of-sight to the passing traffic. Also cheaper than OCR-ing camera footage, and can track vehicles going in both directions, trucks towing trailers, cars with no front plate, etc.

Plate tracking is better for determining direction, and is probably more reliable because TPMS aren't constantly transmitting. You could miss a car if it doesn't have any TPMS info transmitting while it passes your station.

Is phone tracking still possible for the latest iOS or Android phones? I thought my BLE and MAC addresses are randomized, but I don't know much about this beyond that headline. I'm guessing a Stingray type device would still work though.

> Plate tracking is better for determining direction, and is probably more reliable because TPMS aren't constantly transmitting.

And also because direct-sensed TPMS is only one way of implementing TPMS. Other implementations use wheel-speed sensors which are hard wired, not RF.

There are definitely many better ways of doing this, it’s more of a thought experiment.

There are implementations that use the ABS sensors. They don't report the pressure.

Yes, this is trivial and you can do it in about 5 minutes after unboxing your first RTLSDR dongle. Just install rtl_433 and read the commandline help.

Next step is to make a database that recognizes sensors that come past at the same time each day, or correlates groups of four sensors that seem to travel together which probably means they represent the four wheels of the same car, and that's where my software-fu falls flat.

Yeah, TPMS can be a real pain in the ass. And the thresholds it has for reporting true-positives are pretty extreme (~25% low), because the auto industry objected to the cost of accurate sensors.

As far as diagnosing and programming at home, I have a handheld OBD-II reader ($35) that can report TPMS codes like this from the car (without a laptop), and also an OBD-II TPM QuickSet ($120) from ATEQ (a more basic model than the shop had). The QuickSet tool is configured over USB, then attaches to ODB-II to write new TPMS codes into the car. It's useful for swapping between summer and winter wheelsets without a shop.

I’m confused why something is needed. On my Ford I can just “reset” the TPMS after switching wheels from the main computer. I had to do it once because the shop forgot to do it.

Why do you need a whole single thing to do it?

Some cars will auto-learn a new sensor just by driving a mile or so (the Hondas I have had). Others require programming. Why don't all car makers specify the auto-learning ones? No idea. Cost maybe.

The current SUV can be programmed to know 2 sets of five (for summer + winter sets), and you change between them via a switch under the steering wheel. It's common for new owners to get TPMS system errors because the switch got pushed by accident.

> Why don't all car makers specify the auto-learning ones? No idea. Cost maybe.

Because auto-learning ones don't encourage a trip to the dealer, where the customer will go for new tires as well etc.

Like the sibling commenter said, some cars just don't do it automatically (mine included).

There's no point in precise measurement because tire pressure is going to vary widely over temperature and how laden the vehicle is.

Vehicle load changes the contact patch size, not the tire pressure (within reason.)

Over fifty degrees (F) you'll see 5psi change for a passenger car tire (30-40psi.) A 10 psi difference requires a 90 degree differential.

I've routinely seen estimates at 1-2 PSI per 10(f) degree change (depending on tire) and 50+(f) degrees of warming over the first 30 minutes of driving at highway speeds.

That's a change of between 12.5% and 33% depending on tire.

Additional load doesn't change the total volume much - so it's not directly increasing pressure - but it can increase deformation (as you pointed out - contact patch size changes) creating more warming, which will increase pressure.

He could also have used the "mayhem" firmware for HackRF to troubleshoot his problems. Not only does it receive and decode the TPMS data, but it also allows you to spoof and transmit TPMS data.

https://github.com/eried/portapack-mayhem

Here's a tip for everyone. If you have 1 bad TPMS sensor, you're about to have 4 or 5 bad TPMS sensors. Replace all of them at the same time. Most will now tell you if they have low voltage.

Headlights, too. Basically anything that came from the factory in pairs or above.

Pretty much everything on a car lasts between 100 and 400k with a 100k error bar. There is no reason to be replacing the overwhelming majority of stuff in duplicate.

TPMS sensors are almost completely redundant if you have an ABS/TC module they can passively infer low tire pressure.

TPMS is mandated now, in part thanks to urging by their makers.

My 2 year old car doesn't have TPMS sensors, it just uses the ABS system to give a vague "low tire pressure" warning, with no indication of which tire or how low it is.

I prefer the real TPMS sensors despite the higher cost since then when the light comes on, I know which wheel it is, and what the actual pressure is -- if it dropped from 35psi to 25psi, I can make it a few miles to the next exit, but if it's 10psi, I probably need to stop now.

> I prefer the real TPMS sensors despite the higher cost since then when the light comes on, I know which wheel it is, and what the actual pressure is

What car do you have that reports this level of detail? It's much more common for cars to pop a generic "low pressure" icon with zero other details.

Generally the cars that have direct TPMS with sensors in each wheel report pressures (and also throw a warning when one is low) whereas the indirect systems that infer it from rotational speed only throw the warning and give you no more information (eg, which tire is low).

My wife's 2008 Subaru Impreza had the worst of both worlds -- the cost of direct TPMS and no more information than the idiot light.

My Ford Transit van shows the numerical pressure of all 6 tires. Haven't had a low pressure warning yet so I'm not sure what level of detail it gives, but with a few clicks I can pull up the pressures on the instrument panel display.

It also sends the data to Ford so I can see the last read tire pressure on the FordPass app.

Kia Niro also has numerical pressure for four tires. It really helped when I noticed one tire dropped a couple of pounds before the actual TPMS warning on the dash. Took it in and they patched the slow leak. I am now inclined not to buy a car without a numeric display of the pressure in individual tires. It is way too useful a feature.

That’s really cool.

The 2017 Chyrsler Pacifica shows numeric tire pressure at each tire in one of the info screens in the gauge cluster. Also has engine and transmission temperatures. No indicator about which gear the automatic transmission is in though (it does show PRNDL, but not 1-9). I forget what it showed when a tire was low; it might have said which tire it was, or I mighr have flipped to the info page quickly, anyway it notified me promptly when I got a wheel weight embedded in my tire.

Also, when the brake lights go out, it tells you in the info screen, and it says which one. Which is pretty neat.

Might vary by trim, I've got the 'Limited'

One thing a family member has that I'd like is seat belt indicators for every seat in a recent Toyota Highlander. Otoh, I don't like the lane departure warning (it does audible first, the Pacifica is more subtle, it only beeps if you don't respond to the nudges on the wheel)

Lots of higher end cars will show a diagram with the pressure of each tire labeled.

My Toyota Camry reports the pressure reported on each TPMS sensor. Only drawback is I don't know when one matches which tire so when refilling the air, I have to guess a bit.

My Audi RS 5 on the MMI has a screen that shows real time all four pressures, and all four tire temperatures.

2012 Jeep Grand Cherokee and 2015 Jeep Cherokee show tire pressure in each tire.

I my Nissan Leaf (2012) has a screen showing the current reading on each tire.

My 2016 F-150 reports each tire’s pressure.

Hah, my car does have real TPMS sensors but the dashboard display is such that the only thing it can say is a vague "low tire pressure" warning, with no indication of which tire or how low it is. I should get an OBD adapter one of these days.

Speaking from experience, OBD will not necessarily help you here. Something has to put the TPMS data out on the CAN bus. The rudimentary system in my old Corolla does not do this, so the only way to debug a malfunctioning TPMS system is via sdr (or an expensive tool, or a trip to the tire store).

Not just "the" CAN bus, but the one you're sniffing. Many cars have multiple busses that carry different traffic.

A basic mechanical pressure sensor is the much cheaper and more reliable system.

How does a mechanical pressure sensor work? I've only seen electronic ones, how does the mechanical system warn the driver about low tire pressure while driving?

Yeah that’s really frustrating. Different manufacturers have different offerings here. My Toyota has nothing more than the lame “low pressure” warning, but my wife’s company Chevrolet actually shows numeric values for all 4 tires.

Give us the data!!!

That sounds like a preference, which I can respect. It does not IMHO warrant a government mandate for the equipment.

I didn't advocate for or against a TPMS mandate, but I don't want a third party system because a factory TPMS display will be built-into the car's instrument paenl, I don't need to velcro a separate TPMS display to my dashboard and either hardwire it or keep it charged. Plus I know that the OEM system is engineered for that car, I don't have to worry about installing repeaters because there's too much metal between the sensors and the receiver.

But that said, I do believe that the TPMS mandate is worthwhile, I've been alerted a couple times already to a nearly flat tire. (both times due to damage while driving, so I wouldn't have noticed it even if I checked my tire pressure every time I drive the car, which I doubt many people do)

OK, so you're saying that aftermarket TPMS might not be convenient, however, like I said in the original comment, you still have the option to buy the option when buying the car.

Would a pressure reading TPMS system be offered by manufacturers if they already implemented the cheaper passive ABS based system?

As you said previously, TPMS gives a more verbose output than ABS based system. That's a pretty obvious selling point

Is it? My car doesn't offer it as an option, it only offers the ABS based system. Does any car offer the more granular TPMS system if they already offer the ABS based system to fulfill the legal requirement?

Would you be willing to share the make and model of your car?

2021 Honda Accord.

From the owner's manual:

Instead of directly measuring the pressure in each tire, the TPMS on this vehicle monitors and compares the rolling radius and rotational characteristics of each wheel and tire while you are driving to determine if one or more tires are significantly under-inflated.

There's no other TPMS option available for that generation (10th Generation) car at any trim level, not sure about the new 11th Gen coming out this year.

I was kinda in the wrong, that appears to be correct. Honda is advertising the ABS based system as TPMS and is not offering any "upgrades".

What does "ABS" stand for in this context?

It doesn't actually require the ABS (anti-lock braking system), but uses the ABS wheel speed sensors to count wheel rotations, so it's essentially a free way to add TPMS, no additional hardware required since ABS is already required, just need software to track wheel rotations.

https://en.wikipedia.org/wiki/Tire-pressure_monitoring_syste...

Anti-lock braking system

https://en.wikipedia.org/wiki/Anti-lock_braking_system

Eh, I prefer real sensors. My car tells me which tire is low. And I can see current pressures for any wheel if I want. Plus I have sensors on my trailer (which definitely does not have ABS) so I can monitor the pressure in those wheels as well.

Using ABS to passively guess if a tire is low is a big downgrade in functionality.

But a decent upgrade in vehicular privacy!

Things that make you go hmmm...

Triple redundant if you have a $0.99 gauge (presumably all drivers have functional eyeballs).

TPMS sensors are much more precise than ABS/radial speed sensing.

And completely unnecessary. Its absurd to mandate them IMHO.

It was mandated in response to the Firestone scandal/disaster. Over 200 people died because Ford intentionally under-inflated Firestone tires on the Explorer. Also, the tires weren’t very good in the first place.

I guess it got everyone thinking about how dangerous under-inflated tires are on the highway. My guess (and it is a guess) is that radial-velocity pressure estimation wouldn’t have been precise enough and would have either tolerated dangerous under inflation or annoyed with false-positives.

If all your tires are equally low, would ABS-based systems even notice?

This is a really interesting article. One question answered for the author: I believe TPMS sensors have an RFID-style mode, so that handheld programmers can access them without waiting for the slow reporting period.

I have experience with how finicky these sensors can be. I installed a radar detector in my car (legal in my state, and wise considering the unusually aggressive speed enforcement that appears once every few weeks along the highway I drive). I stashed the radar detector's control box in some empty space between the glove box and an air duct. The TMPS receiver module is also located in this area and cannot receive signals while the radar detector is powered on. I assume this is broad-spectrum EMF and I need to layer the control box in aluminum foil.

Consider using a foil tape: https://www.amazon.com/dp/B018RDZ3HG Added bonus of the end result looking vaguely lunar module-esque: https://upload.wikimedia.org/wikipedia/commons/2/2a/Apollo16...

> ...and I need to layer the control box in aluminum foil.

I don't know why, but that sentence is just awesome! Maybe to me it just sounds so MacGyver to me. Either way, very cool!

I wonder, do those sensors have some built-in battery that lasts a long time, but ultimately the whole sensor needs to be replaced due to the electronics being potted-in?

Or is it so low power that it can use some sort of piezoelectric/MEMS power source that charges it as the wheel is spinning?

They are battery powered. The battery lasts a few years, and conserves charge by only reporting pressure every minute after motion is detected.

Yes, they have a battery that lasts a few years. And typically, the battery alone cannot be changed, the whole unit must be replaced.

In my area, all franchised tire shops will refuse to install new tires on your car without also installing brand-new TPMS sensors, regardless of the age of the existing sensor. "Sorry, it's corporate policy."

When I bring my bike to the tire shop for new tires the guy always cuts the nozzle off and places a new one in. Might just be a safety/liability thing. Since they're also made out of rubber, which degrades.

Tire Review says [0]

> the sensors are usually powered by 3-volt lithium ion batteries, but some use 1.25-volt nickel metal hydride batteries. There are developments underway that promise battery-less sensors in the future, having the potential to dramatically change TPMS markets.

Also, YouTube has a number of videos on how to change out the batteries

[0] https://www.tirereview.com/changing-tpms-sensor-batteries/

Battery shall last for 10 years. Ideally you need to replace the tire before the battery gets empty.

Yep, it's a small battery and low-power device.

I think it's cute he assumed he got a bad sensor replaced.. following the story, it's more probable the shop replaced two good sensors and never the actual bad one until the end. Seems far more reasonable explanation of the whole episode.

After the initial trip to the tire shop, 2 of the sensor IDs that were previously working were still working. And I had 2 brand new valve stems. So they definitely changed out the bad one, along with another one. I just got super unlucky and one of the new sensors was defective.

The author more or less watched them swap the sensor that had initially been replaced.

(and had the ids of the remaining sensors)

Somewhat related, my post about receiving TPMS signals, but without SDR: https://milek7.pl/tpmsreceiver/

Never thought about it, but just checked on amazon, TPMS Reset Tool for my car costs 12 bucks, I was getting charged when I swapped tires. Sounds like a way to save money.

Yep. GM cars, for sure, have a cheap tool that makes it trivial to reprogram TPMS. Some cars will do it themselves, after you swap on a new set of wheels and drive a few miles.

I suspect most cars have a manual process available. Mine does, it takes a while though and involved letting the air out of the tire for 30 seconds, and then setting each tire to a different pressure - in my case the car wants to know which tire is in which position.

Other cars that don't care about that usually just have a button on the dash you can press to start the relearn process.

Now that makes me wonder, would the Flipper Zero be able to capture that kind of data? I'll have to buy one someday..

TPMS sensors. A solution to a problem you never had. Congratulations. They have batteries, so it's a gift that keeps on giving.

Speak for yourself. TPMS is a great feature. Ever drive on a highway that's so poorly-maintained that you find yourself wondering if you're getting a flat? Ever find yourself miles from home with a slow air leak that you need to keep an eye on to ensure that you can make it to the shop safely? Do you enjoy crawling around on your hands and knees with a tire gauge, contemplating the uncertainty principle while you wonder how much air you just let out of your tire while trying to check it?

I've never owned a TPMS-equipped car that wasn't accurate to within +/- 2 PSI in the 30-35 PSI range, and won't be buying any such cars in the future. I see a lot of people complaining about crappy TPMS implementations, but that's something to blame your cheap-ass automaker for, not the technology itself.

There is also indirect method - ECU precisely comparing each wheel's rotation speed, with assumption that lower-pressure tire would have smaller outer radius, thus slightly higher angular velocity. This method is somewhat common with European cars.

It's very cheap (assuming car already has rotation sensors for ABS, and adding a software routine doesn't cost much either), and maintenance-free.

But there are drawbacks, too - it doesn't detect all tires deflating at the same rate. And also, ECU has to be very conservative to avoid false-positives, average a lot, pause comparison when turning, etc. As a result, you only get the tire pressure warning like 10 minutes later that dTPMS would've flagged it.

The VAG system circa 2014 - which i think is a Bosch system used by many manufacturers unchanged, i can’t remember the name of the system but i recall it was version 9.5 of Bosch’s system - was able to notify me of a fairly rapid puncture (hit a pothole at high speed) within around 300 yards. The tyre deflated slowly enough to continue for another 4 miles (albeit at much lower speed) so there would only have been a few PSI lost at the time it triggered.

On the whole in that car (Golf R mk7) it did seem pretty switched on at noticing pressure loss from a slow leak i had after a tire replacement one time, which was handy because the tyres were pretty low profile that meant visual checks were utterly useless. It’d look perfectly fine at 10psi in a tire that should be at 34psi.

One other benefit of the ABS system is that when it goes wrong and the money light comes on, the user’s probably more likely to respond to a “brake service now!” Type message than a “TP-something or was it TS or oh i dont know but the car still seems to drive fine so…”

>contemplating the uncertainty principle while you wonder how much air you just let out of your tire while trying to check it?

This is just a stupid tax on people unable to discern the difference between theory and practice and if anything life needs more of these taxes.

It's absolutely a problem I've had. I drove on a flat for several miles one winter because I thought the sound was just snow packed into the wheel-well, and driving on snow masked the funny handling characteristics of a flat tire.

By the time I got where I was going, the sidewalls were wrecked. TPMS would've saved me a tire AND a bunch of hassle of getting it replaced; the puncture was small and would've been easy to plug if I'd only known to look for it.

I knew a Firestone / Ford Explorer widow. She had a flock of kids.

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

How would TPMS have helped the Firestone/Ford issue? The tires weren't spontaneously losing pressure; Ford was spec'ing a low tire pressure and the tread was separating. I'm generally supportive of TPMS but struggling to figure out how your comment is responsive to the grandparent comment.

Tires do spontaneously lose tire pressure. 1-3 psi/month.

There was no margin on tire pressure. TPMS would absolutely have saved lives. General public runs consistently low tire pressure. Source: I am a member of general public and consistently forget to top up. Also, paid my way through college in the 1980s in a gas station back when full service was a thing.

Advocating for blindly making things "safer" with no regard for tradeoffs is like littering in the park. If a few people do it it's no big deal. When everyone does it you wind with bloated cars we can't see out of loaded full of tech that drives up cost, or a trashed park. Thanks for doing your part.

And as the other guy mentioned, TPMS doesn't help you when the spec for the pressure is what's wrong.

TPMS is very important with run-flat tires because you cannot easily tell if one has a puncture or is low on air by looking at it - they hardly bulge at all.

I wonder if you can get a sensor emulator that plugs into a cigarette lighter and you can program the car to read from that. It'd be illegal but you could totally find people who would pay for that.

You can just ignore or tape over the dashboard light instead.

TPMS’s should go into hibernation when there’s no movement. I wonder if battery packs can be designed to last a lifetime.

I like contents about hacking on this blog. Recommend to check other posts.

i am just amazed how much jobs were created by introducing this sensor in cars.

I have an RTL-SDR that collects sensor data via rtl_433 [0] and publishes it to MQTT, which I use for temperature and contact sensors. I found it interesting that I pick up a fair amount of TPMS data from (what I presume are) people driving by.

    {"time":"2022-08-03 08:25:13","model":"Schrader","type":"TPMS","flags":"ab","id":"555551E","pressure_kPa":267.5,"temperature_C":57.0,"mic":"CRC"}
    {"time":"2022-08-06 04:53:23","model":"Schrader","type":"TPMS","flags":"d5","id":"2F656AA","pressure_kPa":585.0,"temperature_C":120.0,"mic":"CRC"}
    {"time":"2022-08-06 06:15:29","model":"Schrader","type":"TPMS","flags":"af","id":"4BAAC5B","pressure_kPa":227.5,"temperature_C":35.0,"mic":"CRC"}
    {"time":"2022-08-08 10:24:43","model":"Schrader","type":"TPMS","flags":"af","id":"553AAD5","pressure_kPa":232.5,"temperature_C":120.0,"mic":"CRC"}
    {"time":"2022-08-08 10:35:39","model":"Schrader","type":"TPMS","flags":"5a","id":"AAB8576","pressure_kPa":452.5,"temperature_C":43.0,"mic":"CRC"}
    {"time":"2022-08-08 10:58:22","model":"Schrader","type":"TPMS","flags":"ad","id":"6FF5667","pressure_kPa":427.5,"temperature_C":56.0,"mic":"CRC"}
    {"time":"2022-08-09 21:34:49","model":"Schrader","type":"TPMS","flags":"6a","id":"BAD22B2","pressure_kPa":212.5,"temperature_C":132.0,"mic":"CRC"}
    {"time":"2022-08-09 23:31:35","model":"Schrader","type":"TPMS","flags":"6a","id":"AB5E5B6","pressure_kPa":545.0,"temperature_C":163.0,"mic":"CRC"}
    {"time":"2022-08-10 16:49:55","model":"Schrader","type":"TPMS","flags":"57","id":"B56AED6","pressure_kPa":427.5,"temperature_C":36.0,"mic":"CRC"}
    {"time":"2022-08-11 00:58:24","model":"Schrader","type":"TPMS","flags":"ab","id":"DF44AAB","pressure_kPa":452.5,"temperature_C":187.0,"mic":"CRC"}
    {"time":"2022-08-11 01:36:15","model":"Schrader","type":"TPMS","flags":"aa","id":"AB55552","pressure_kPa":432.5,"temperature_C":35.0,"mic":"CRC"}
    {"time":"2022-08-13 08:27:24","model":"Schrader","type":"TPMS","flags":"54","id":"5555553","pressure_kPa":425.0,"temperature_C":120.0,"mic":"CRC"}
    {"time":"2022-08-16 10:48:29","model":"Schrader","type":"TPMS","flags":"aa","id":"B552AAA","pressure_kPa":425.0,"temperature_C":123.0,"mic":"CRC"}

(Note: IDs munged just in case they're sensitive). I can't speak to the quality of data -- for what it's worth I do live on a regional road with a high speed limit, so it's understandable there would be some hot tires. However theses could also just be poor quality sensors, bad signals, or bugs in rtl_433.

Even aside from the obvious things like carrying around and using apps on a cell phone, it's amazing to realize how much information everyone leaks just going about their day. I've not investigated anything about how frequently or reliably these signals are sent, but it does seem feasible this could get used for vehicle presence detection or even short-range tracking.

[0] https://github.com/merbanan/rtl_433

We used to have this cool thing called “sense”. It was neat. When your tire was low you could “sense” it through the steering wheel by holding onto it. Then you got this feeling something was amiss and you “looked” at your tires. Hmm it didn’t look right. So you pulled out this 2 dollar device called a pressure gauge and checked the pressure. It was pretty sweet. Had the extra benefit of tire changes being 25 dollars cheaper per tire as well. It had one major flaw though. You had to not be a idiot. :/

agree - mandated sensors are a playground for the surveillance set; make them readily available, sure.