Tire Pressure Sensor IDs: Why, Where and When (2015)
tomorrowstechnician.com
tomorrowstechnician.com
Aside: I'll never get another chance to share this, so please forgive the "humor".
Once my wife was driving, with me as her passenger when, the car's TPMS indicator came on. She was concerned and said "There's this 'TPMS' warning light here. What does that mean?".
Without even thinking I said "That probably means something." Likely the greatest accidental fitting of words to an initialism I've ever made in my life.
For anyone else looking to do the same with it this project is great: https://github.com/merbanan/rtl_433
rtl_433 has been great. The ability to capture unknown-to-it signals and build decoders on the command line is really nice. I've got some cheapie driveway motion sensors that I built a decoder for. It was exceptionally easy and all the config was runtime.
And of course there are cheap sensors you can find online for your own temperature probes.
That’s why it’s a FMVSS requirement now.
There are secure TPMS implementations, e.g. ABS sensor based systems.
This is revisionist history through the lens of screeching people on Reddit.
Back in the old days you didn't need to "check your tires" because it's flagrantly obvious visually and in terms of handling when a tire with a 65 or 75 aspect ratio is low.
The reason we have a bunch more requirements on tires is because of all the finger pointing that ensued as a result of the Firestone Explorer debacle suddenly made formerly irrelevant few-psi differences in pressure very important. TPMS is there because you can't get a good visual read on lower profile tires until they're quit low. If you're not oblivious it won't matter you'll feel the vehicle handling funny long before they actually get low enough to cause problems though.
What "solved" blowouts was changes in construction. They started putting a couple extra belts into passenger car tires in the mid 00s. It mostly has to do with cap improvements that help prevent the sidewall from opening up at the shoulder.
Back in "the day" (so like 80s on down) everyone ran their tires to failure (usually bald, but often blowout as well) as a matter of normal practice, bought used tires left and right and blowouts were pretty common, even more common back in the really old days of tubes. It didn't reliably cause an accident unless you behaved hysterically in response, hence why everyone felt fine doing it. But that was so long ago ago, nobody much remembers it, nobody wrote about it on the internet and therefore it doesn't exist for the purposes of online discussion.
Time for me to stop internetting, enternal summer, etc.
> Back in "the day" (so like 80s on down) everyone ran their tires to failure (usually bald, but often blowout as well) as a matter of normal practice, bought used tires left and right and blowouts were pretty common, even more common back in the really old days of tubes. It didn't reliably cause an accident unless you behaved hysterically in response, hence why everyone felt fine doing it.
Yeah, tire technology wasn't great then. And yes, there were people that ran bald tires. But there are still people today that don't care about bald tires. Depends on which side of town you're on. The common way people were measuring tire tread in the 80s, if they cared, was with Lincoln's head on a penny. But also people didn't drive as aggressively as they do now, because 80s cars were slow as shit compared to what people are driving today or even in the 2000s.
Probably why the issue came about with the Ford Explorer, a early widespread SUV
On bias-ply tires from ‘60s, sure. You’re not going to visually check tire pressure on radials, at least not with any accuracy.
Back in "the day" (so like 80s on down) everyone ran their tires to failure (usually bald, but often blowout as well) as a matter of normal practice,
That’s just old man “kids today!” bullshit. I was an auto mechanic in the ‘80s, and the only people that did that were very poor or very stupid.
I have always wondered if it is the lack of sidewall on a 225/45R17.
I did notice in time though, somehow. The tire shop also couldn't find a reason for the flat, so they simply remounted it, filled it, and sent me on my way.
I've had a valve core get stuck open in a way that was released by poking at it. And the little plastic cap is amazingly good at holding the tire pressure in too. Sometimes rebooting the computer is the right fix.
I consider that a worthy tradeoff though, I can just check the pressure once in a while and I get to save money on my winter wheel set.
But anecdotally, we were driving through Chicago in the family Subaru Forester, and got a huge gash in one tire. The Soob has so much automation in its drivetrain, that it still handled OK enough and we didn't notice there was a problem until the TPMS light came on. We had to cross a couple lanes of very heavy, fast traffic, to get off the road.
https://en.wikipedia.org/wiki/Tire-pressure_monitoring_syste...
It has its own shortcomings, but in my opinion they're all relatively minor and it does the job of warning the driver of potential pressure problems without wireless or in-tire sensors that require replacement.
EDIT, never mind, I wasn't seeing "indirect" in the comments but now that I look I do see "ABS", which is what iTPMS depends on for determining wheel speed.
A compression test for whether manual transmission engine is capable of cylinder combustion.
There's a third incident like that too, but since I figured out that it had been flat when I started out, that I could've prevented it by looking at the tires (with a flashlight, cause it was dark).
In the old days, you had to drive a couple miles to be certain you really had a flat, at which case things were damaged.
1. Data is not signed.
So data can be easily spoofed and jam up the real sensor's transmissions.
2. Serial number is not obfuscated or in a reduced serial number set.
This allows TPMS trackers to be placed at high vehicle through areas and uniquely track cars. Is dying out due to Flock and ALPRs.
3. Some cars, primarily luxury, will force slow you down to 15mph, honk horns, and go into limp mode.
Note this is trusting unencrypted, unsigned, cleartext data. This is a terrible idea, and you cant turn it off.
I'm surprised some company hasn't sold a "gun" to law enforcement that will disable cars remotely this way.
I can see them doing it if the data goes from good to bad and then the bad persists over a key off cycle though.
Look at what happens if you spoof and spam a 0kPa event on various cars.
Some show a tpms warning. Some luxury ones do limp mode.
Source? I can't find any reference. It looks like you're hallucinating.
Nah, I'm not providing exploit code to something unpatchable.
But if you use a rtlsdr, read, decode, modify, and then use a Hackrf to generate the waveform... Yeah, it works.
No ai. No hallucination. Just good at signals.
I'm unsure of all the different cars. Its all how a blowout report is handled by the ECU.
I know my cars, Toyotas Prius 2013 and rav4 2017 only do the light. No limp mode.
Ive tested it on a friends Benz, and that one gets positively rude. Limp mode, cabin buzzer, console blinking lights.