[HN Gopher] Solving my truck's TPMS sensor problem with the help...
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Solving my truck's TPMS sensor problem with the help of an RTL-SDR
dongle
Author : zdw
Score : 74 points
Date : 2022-08-22 16:19 UTC (6 hours ago)
(HTM) web link (www.downtowndougbrown.com)
(TXT) w3m dump (www.downtowndougbrown.com)
| garaetjjte wrote:
| Somewhat related, my post about receiving TPMS signals, but
| without SDR: https://milek7.pl/tpmsreceiver/
| throw7 wrote:
| TPMS sensors. A solution to a problem you never had.
| Congratulations. They have batteries, so it's a gift that keeps
| on giving.
| jollyllama wrote:
| 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.
| loeg wrote:
| You can just ignore or tape over the dashboard light instead.
| BuffaloBagel wrote:
| I knew a Firestone / Ford Explorer widow. She had a flock of
| kids.
|
| https://en.wikipedia.org/wiki/Firestone_and_Ford_tire_contro...
| loeg wrote:
| 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.
| throwaway0a5e wrote:
| 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.
| CamperBob2 wrote:
| 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.
| nousermane wrote:
| 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.
| CraigJPerry wrote:
| 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..."
| throwaway0a5e wrote:
| >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.
| myself248 wrote:
| 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.
| lttlrck wrote:
| 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.
| loeg wrote:
| 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.
| spockz wrote:
| 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?
| loeg wrote:
| Like the sibling commenter said, some cars just don't do it
| automatically (mine included).
| chiph wrote:
| 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.
| throwaway0a5e wrote:
| There's no point in precise measurement because tire pressure
| is going to vary widely over temperature and how laden the
| vehicle is.
| landr0id wrote:
| 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.
| jaywalk wrote:
| 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.
| doubled112 wrote:
| 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.
| ce4 wrote:
| The sensors should stay off at rest though (There's
| acceleration sensors in the that activate them above a
| certain rpm value)
| function_seven wrote:
| 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.
| joncrane wrote:
| 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.
| pottertheotter wrote:
| 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.
| bonestamp2 wrote:
| Yes, some cars use the abs sensors to detect rotation
| differences and estimate a low tire pressure scenario.
| jdeibele wrote:
| 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.
| rconti wrote:
| 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).
| jsight wrote:
| Newer Teslas are using Bluetooth Low Energy. I suspect that
| some other manufacturers might do something similar.
| myself248 wrote:
| 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.
| mc32 wrote:
| 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.
| function_seven wrote:
| 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.
| kube-system wrote:
| > 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.
| landr0id wrote:
| There are definitely many better ways of doing this, it's
| more of a thought experiment.
| sokoloff wrote:
| Yes, it's possible.
| https://m.youtube.com/watch?v=TDYoo7TGNcw&t=7m45s
| ruskyhacker wrote:
| Yeah, you absolutely can - speaking from experience.
| [deleted]
| phkahler wrote:
| 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.
| tedmid wrote:
| TPMS sensors are much more precise than ABS/radial speed
| sensing.
| rootusrootus wrote:
| 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.
| aaaaaaaaata wrote:
| But a decent upgrade in vehicular privacy!
|
| Things that make you go hmmm...
| throwaway0a5e wrote:
| Triple redundant if you have a $0.99 gauge (presumably all
| drivers have functional eyeballs).
| Johnny555 wrote:
| 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.
| NullPrefix wrote:
| How does a TPMS mandate existence or inexistence prevent you
| from getting that option when buying the car or installing
| the aftermarket version?
| Johnny555 wrote:
| 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)
| NullPrefix wrote:
| 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.
| Johnny555 wrote:
| Would a pressure reading TPMS system be offered by
| manufacturers if they already implemented the cheaper
| passive ABS based system?
| NullPrefix wrote:
| As you said previously, TPMS gives a more verbose output
| than ABS based system. That's a pretty obvious selling
| point
| Johnny555 wrote:
| 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?
| NullPrefix wrote:
| Would you be willing to share the make and model of your
| car?
| Johnny555 wrote:
| 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.
| NullPrefix wrote:
| 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".
| aaaaaaaaata wrote:
| What does "ABS" stand for in this context?
| Johnny555 wrote:
| 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...
| grzm wrote:
| Anti-lock braking system
|
| https://en.wikipedia.org/wiki/Anti-lock_braking_system
| loeg wrote:
| > 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.
| slaw wrote:
| 2012 Jeep Grand Cherokee and 2015 Jeep Cherokee show tire
| pressure in each tire.
| rconti wrote:
| 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.
| UniverseHacker wrote:
| Lots of higher end cars will show a diagram with the
| pressure of each tire labeled.
| pkaye wrote:
| 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.
| Cerium wrote:
| I my Nissan Leaf (2012) has a screen showing the current
| reading on each tire.
| GiorgioG wrote:
| My 2016 F-150 reports each tire's pressure.
| Johnny555 wrote:
| 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.
| loeg wrote:
| That's really cool.
| protomyth wrote:
| 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.
| mastax wrote:
| 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.
| jakear wrote:
| A basic mechanical pressure sensor is the much cheaper and
| more reliable system.
| Johnny555 wrote:
| 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?
| el_benhameen wrote:
| 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).
| kube-system wrote:
| Not just "the" CAN bus, but the one you're sniffing. Many
| cars have multiple busses that carry different traffic.
| tedmid wrote:
| 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!!!
| nwellinghoff wrote:
| 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. :/
| mistrial9 wrote:
| agree - mandated sensors are a playground for the surveillance
| set; make them readily available, sure.
| Ristovski wrote:
| 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?
| andrewia wrote:
| They are battery powered. The battery lasts a few years, and
| conserves charge by only reporting pressure every minute after
| motion is detected.
| bityard wrote:
| 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."
| aequitas wrote:
| 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.
| loeg wrote:
| Yep, it's a small battery and low-power device.
| hulitu wrote:
| Battery shall last for 10 years. Ideally you need to replace
| the tire before the battery gets empty.
| WorkerBee28474 wrote:
| 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/
| IronWolve wrote:
| 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.
| ars wrote:
| 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.
| rootusrootus wrote:
| 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.
| bandyaboot wrote:
| 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.
| loeg wrote:
| Oh, that's smart. I just reprogram when I swap.
| 1970-01-01 wrote:
| 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.
| powerhour wrote:
| Headlights, too. Basically anything that came from the factory
| in pairs or above.
| throwaway0a5e wrote:
| 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.
| andrewia wrote:
| 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.
| itsyaboi wrote:
| 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...
| mxuribe wrote:
| > ...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!
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