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-   -   Reading Tire Pressures Real Time via TPMS Sensors (https://www.ft86club.com/forums/showthread.php?t=113385)

Bluesman62 11-30-2016 12:16 PM
Reading Tire Pressures Real Time via TPMS Sensors
 
My new 2017 Kia Sportage will actually display in real time (or close to it) the pressure of each tire via a display on in the gauge cluster. Assuming that works off of the TPMS. Very cool feature.

Would love to be able to read the tire pressures in real time in my BRZ rather then just having an idiot light in the dash. Besides the reprogramming and hand tools which would not do you good while actually driving, does anyone know of a system that can read the TPMS sensors or plug into the OBD2 port to display that info in real time?

The only thing I found are those systems which have the sensors in the value stem caps and has a display that plugs into 12V port.

Cole 11-30-2016 12:24 PM
I believe @Shiv@Openflash was working on it, but I haven't seen any actual progress on it yet. But then again, I'm not following that too closely. Torque may be able to do it?

JDM4E 11-30-2016 01:45 PM
I like that feature too. Subscribed.
I think that perhaps changing the sensors will be needed. There quite a lot aftermarket systems available, they even can monitor the air temperature which is great I think and it is the way I would go.

Bluesman62 11-30-2016 02:20 PM
Quote:
Originally Posted by JDM4E (Post 2806316)
I like that feature too. Subscribed.
I think that perhaps changing the sensors will be needed. There quite a lot aftermarket systems available, they even can monitor the air temperature which is great I think and it is the way I would go.
Ours do. I was just at the dealer to have the sensors in my wheels registered with my car (long story! The Story )

While the tech was doing it he showed me all the parameters the sensors were sending to the car which included temperature. Has was using a (very expensive I assume) Snap-On programmer to check everything.

JDM4E 11-30-2016 05:34 PM
Quote:
Originally Posted by Bluesman62 (Post 2806348)
Ours do. I was just at the dealer to have the sensors in my wheels registered with my car (long story! The Story )

While the tech was doing it he showed me all the parameters the sensors were sending to the car which included temperature. Has was using a (very expensive I assume) Snap-On programmer to check everything.
Great info. Now the harder bit - how to read that data in a car :iono:

sirsol66 12-01-2016 12:24 PM
Your TPMS sensors send a data packet every 10 seconds or so when they see motion. As mentioned, they send temperature, movement (yes or no), and individual pressure. We lack the secondary ECU for autolocation so they dont know where on the vehicle they are. Everything goes through the CANBUS setup so getting the reading shouldnt be difficult honestly. It just comes down to programming OFT or something to actually pull that information.

You can see all that information with tech stream (non lite) or similar equipment.

Icecreamtruk 12-01-2016 12:47 PM
Can it be possible to read it out thru torque if we know where they are being transmitted (custom PIDs in torque)?

Clipdat 12-01-2016 12:51 PM
@Shiv@Openflash

iamrich83 03-08-2018 08:07 AM
Has there been any progress on this? I tried searching...

Racecomp Engineering 03-08-2018 11:11 AM
I thought about this a while back. Sounds like a project for a RaspberryPi or Arduino pro (which I am not).

- Andrew

timurrrr 06-09-2021 04:29 PM
Quote:
Originally Posted by ermax (Post 3440059)
Current gen has pressure and temps via CANbus but I’ve never found a way to read them. Techstream can read them so I know it’s possible.
If anyone found the CAN or OBD-II PIDs for tire pressures and temps, let me know!

gpvecchi 06-09-2021 04:49 PM
Techstream reads tires pressure, so this data is accessible by OBD.

LimitedSlip 06-09-2021 07:40 PM
A ScanGauge can read tire pressure and temperature from the OBD port. It only updates every 3 to 5 minutes but I don't know how often the TPMS sensors actually report data. But how often do you realistically need an update?

Here's a thread with more from 2013:

https://www.ft86club.com/forums/showthread.php?t=28374

And an update from 2018:

https://www.ft86club.com/forums/showthread.php?t=128103

timurrrr 06-09-2021 08:40 PM
NICE, thanks for digging this up!

So if I'm reading https://www.scangauge.com/toyota-tpms-method-2/ correctly,
the bytes that get sent over the CAN bus for the request are 0x07502A2190.

I'll need to spend some time trying to figure out how to enter it into e.g. RaceChrono.
Dang, I just swapped took my daily wheels with TPMS off the car and put AutoX wheels on, now I can't wait to swap back.

I know that for fuel level the RaceChrono setup is
Quote:
Channel: Fuel level (L)
OBD-II header: 0x7C0
PID: 0x2129
Equation: A/2
Here's the ScanGauge setup for the same data:
Quote:
Originally Posted by pkny (Post 717589)
Working code for FR-S/BRZ/86:
Code:
Gauge                          Unit          TXD                  RXF                      RXD      MTH                      Note
...
Precise Fuel Level        %        07C02129      046105290000    2808    000100010000    Faster refresh rate
...
07C02129 looks like 0x07C0 + 0x2129.

So 0x07502A2190 could be something like
OBD-II header: 0x750
PID: 0x2A2190
?

Also will need to read ScanGauge manuals on what all those RXF/RXD/MTH codes mean, so that we can figure out what scale/offset to use.

If somebody figures it out before me, we will all appreciate if you post your findings here :)

timurrrr 06-09-2021 08:52 PM
From the manual:

Quote:
Step 3 - Enter the RXF Data
The RXF Screen is the entry for the receive filter.
This value tells the ScanGauge what to look for in
a response from the vehicle’s computer.
Also, some of the entries tell the ScanGauge how
to display the data. Choices are integer, tenths,
hundreds, hexadecimal or on/off. There are also
some fields that can turn any trip value into a
gauge.

...

Step 4 - Enter the RXD Data
The RXD Screen is the entry that tells the
ScanGauge where the data and its size are in the
response.

...

Step 5 - Enter the MTH Data
The MTH (math) screen tells the ScanGauge the math needed to scale and/or offset the value received
I sense some trickery in these :D

ermax 06-10-2021 12:48 AM
Quote:
Originally Posted by LimitedSlip (Post 3440246)
It only updates every 3 to 5 minutes but I don't know how often the TPMS sensors actually report data.
This explains why I never found anything when sniffing the traffic. It becomes a needle in a haystack if it only refreshes every 3 mins. Thanks for the info. I’m going to resurrect my RPi and take another stab at this.

CrowsFeast 06-10-2021 08:54 AM
Quote:
Originally Posted by timurrrr (Post 3440272)
From the manual:



I sense some trickery in these :D
Curious if there's anything that operates like the E46 'temp gauge' does!
(The temp gauge has a very large range of values where it will display straight up without moving. The thermostat housing has a heating element in it to artificially open the thermostat at lower temperatures to provide greater cooling to the car in certain conditions. Basically they run the engine hotter/colder depending on whether you're driving for fuel economy or performance and don't want customers constantly going to the dealership because their coolant temp is constantly changing.)

bentanic 08-04-2021 09:59 PM
Hey guys I've had luck with the carista app, I'll post a picture later.
https://imgur.com/a/X0eOpOu
https://imgur.com/a/EP0X5No
https://imgur.com/a/EP0X5No

timurrrr 01-12-2022 02:34 AM
Quote:
Originally Posted by timurrrr (Post 3440266)
So if I'm reading https://www.scangauge.com/toyota-tpms-method-2/ correctly,
the bytes that get sent over the CAN bus for the request are 0x07502A2190.

[...] 0x07502A2190 could be something like [this in RaceChrono]:
OBD-II header: 0x750
PID: 0x2A2190
?
I finally found some time to play with the CAN bus in my '17 BRZ, and unfortunately couldn't easily get this data.

I tried sending 0x2A2190 to the CAN ID 0x750 and didn't get any responses.
I heard TPMS data isn't available immediately after starting the engine,
so I drove around a medium-sized block before doing trying those requests,
and kept the engine running throughout.

I tried both with RaceChrono, and using my own DIY device plugged into the CAN bus.
As a sanity check, I tried sending OBD protocol requests with standard PIDs using my DIY device and I did get the correct responses.

One possible theory is that I should just drive more after starting the engine before trying to send those requests.
Or maybe I the requests I was sending were just a little off the correct ones...

:iono:

geraldjust 01-12-2022 03:45 AM
Quote:
Originally Posted by timurrrr (Post 3495983)
I finally found some time to play with the CAN bus in my '17 BRZ, and unfortunately couldn't easily get this data.

I tried sending 0x2A2190 to the CAN ID 0x750 and didn't get any responses.
I heard TPMS data isn't available immediately after starting the engine,
so I drove around a medium-sized block before doing trying those requests,
and kept the engine running throughout.

I tried both with RaceChrono, and using my own DIY device plugged into the CAN bus.
As a sanity check, I tried sending OBD protocol requests with standard PIDs using my DIY device and I did get the correct responses.

One possible theory is that I should just drive more after starting the engine before trying to send those requests.
Or maybe I the requests I was sending were just a little off the correct ones...

:iono:
i actually got TPMS out of the can data from these cars. But its not as simple as sending some bytes and getting the return back. I can give ya a hint. its basically how Multi-Frame Message. If you google that you will get a semi aquatineace on how it works.

https://www.geraldjustprojects.com/w...2.42.49-AM.png

BTW responses should be in 0x758

NoHaveMSG 01-12-2022 11:53 AM
Quote:
Originally Posted by geraldjust (Post 3495988)
i actually got TPMS out of the can data from these cars. But its not as simple as sending some bytes and getting the return back. I can give ya a hint. its basically how Multi-Frame Message. If you google that you will get a semi aquatineace on how it works.


BTW responses should be in 0x758
Do you have any idea how much us track day guys would love you long time if you came out with a kit for this?

geraldjust 01-12-2022 01:44 PM
Quote:
Originally Posted by NoHaveMSG (Post 3496054)
Do you have any idea how much us track day guys would love you long time if you came out with a kit for this?
oh a kit? its already a gauge i sell lol. its just one out of many features the gauge has.

NoHaveMSG 01-12-2022 01:49 PM
Quote:
Originally Posted by geraldjust (Post 3496101)
oh a kit? its already a gauge i sell lol. its just one out of many features the gauge has.
I haven't been on your website in a while but it appears I need to do some shopping :D

Pat 01-12-2022 01:52 PM
Have you guys ever compared TPMS readings with readings from a high-quality traditional gauge? I have a few times and there is often error of two or more PSI. In my experience TPMS is not exactly that useful at the race track.
Hopefully TPMS sensors have become more accurate since I checked them. Or maybe they can be recalibrated somehow. I don't know much about them. But I think it's important to recognize there can be significant inaccuracies in them.

NoHaveMSG 01-12-2022 01:55 PM
Quote:
Originally Posted by Pat (Post 3496104)
Have you guys ever compared TPMS readings with readings from a high-quality traditional gauge? I have a few times and there is often error of two or more PSI. In my experience TPMS is not exactly that useful at the race track.
Hopefully TPMS sensors have become more accurate since I checked them. Or maybe they can be recalibrated somehow. I don't know much about them. But I think it's important to recognize there can be significant inaccuracies in them.
I don't expect it to be perfect but as long as it has been correlated to a known gauge then it is still useful. The one in my truck is pretty accurate to my Blue Point gauge. My Milwaukee compressor's gauge is off almost two PSI.

braz009 01-12-2022 02:16 PM
Quote:
Originally Posted by geraldjust (Post 3496101)
oh a kit? its already a gauge i sell lol. its just one out of many features the gauge has.
What is your website where we can purchase these?

Sent from my Pixel 4a (5G) using Tapatalk

NoHaveMSG 01-12-2022 02:26 PM
Quote:
Originally Posted by braz009 (Post 3496114)
What is your website where we can purchase these?

Sent from my Pixel 4a (5G) using Tapatalk
https://www.geraldjustprojects.com/p...category/cars/

geraldjust 01-12-2022 02:43 PM
Quote:
Originally Posted by Pat (Post 3496104)
Have you guys ever compared TPMS readings with readings from a high-quality traditional gauge? I have a few times and there is often error of two or more PSI. In my experience TPMS is not exactly that useful at the race track.
Hopefully TPMS sensors have become more accurate since I checked them. Or maybe they can be recalibrated somehow. I don't know much about them. But I think it's important to recognize there can be significant inaccuracies in them.
yeah i was worried about that too. but the sensors have a .5psi resolution. i also did a small log comparing temps too. and noticed the psi increases in a linear fashion. Keep in mind that the sensors are Absolute pressure so if your off like by 2psi most likely you might be in a higher elevation point. traditional gauges are relative pressure then absolute.

Edit:
I see your from denver colorado! see there's your problem lol. your around 5.2k feet above sea level lol your getting around 12psi ambient. while were close to sea level we see 14.6psi so that's where your discrepancy comes from.

Pat 01-12-2022 03:08 PM
While that might explain some of the discrepancies, it doesn't explain all of them. I've still seen meaningful differences between sensors on the same vehicle at a fixed altitude.
Also, explaining the difference is altitude doesn't really fix the problem. It's still a problem many people have to account for if they want accurate readings. I don't understand why people are so reluctant to check tire pressures manually. It takes almost no time or effort.

NoHaveMSG 01-12-2022 03:16 PM
Quote:
Originally Posted by Pat (Post 3496138)
While that might explain some of the discrepancies, it doesn't explain all of them. I've still seen meaningful differences between sensors on the same vehicle at a fixed altitude.
Also, explaining the difference is altitude doesn't really fix the problem. It's still a problem many people have to account for if they want accurate readings. I don't understand why people are so reluctant to check tire pressures manually. It takes almost no time or effort.
I do check them manually. The problem is I would like to have an idea of what my tire pressures are peaking at as what I am reading in the pits isn't 100% accurate either because of a long cooldown lap at the track I frequent the most. I am interested more for the data and to have a live reference while driving.

timurrrr 01-13-2022 01:04 AM
Quote:
Originally Posted by geraldjust (Post 3495988)
i actually got TPMS out of the can data from these cars. But its not as simple as sending some bytes and getting the return back. I can give ya a hint. its basically how Multi-Frame Message. If you google that you will get a semi aquatineace on how it works.

...

BTW responses should be in 0x758
This is a great pointer!
We would all really appreciate it if you could just share the exact request / response protocol.
I'm going to add it to my GitHub anyways, but you can just save everyone some time :)

I promise to read more into the details of how Multi-Frame Messages work!
I find "learn by studying an example" to be more effective than
"learn by first solving a puzzle that requires you to already know what you want to learn to solve it".

Also curious if you've confirmed if the same message format is working on the 2022 cars.

Quote:
Originally Posted by Pat (Post 3496104)
Have you guys ever compared TPMS readings with readings from a high-quality traditional gauge? [...] But I think it's important to recognize there can be significant inaccuracies in them.
Totally. I definitely wouldn't rely solely on them, but they should give you a ballpark trend how much your tires gained in PSI since the start of the session.

Quote:
Originally Posted by geraldjust (Post 3496124)
Keep in mind that the sensors are Absolute pressure
Interesting data!

Quote:
Originally Posted by geraldjust (Post 3496124)
yeah i was worried about that too. but the sensors have a .5psi resolution
I have seen two different sensors at the exact same ambient conditions reading 2–3 psi off each other,
even though the same pressure gauge measured the same pressure from both tires.
So "0.5 psi resolution" doesn't necessarily mean "0.5 psi precision".
But again, as long as you can see the general trend...

Quote:
Originally Posted by geraldjust (Post 3495989)
So i made mine also check temp too.
This is perhaps even more interesting to log!

timurrrr 01-13-2022 01:05 AM
Quote:
Originally Posted by Pat (Post 3496138)
While that might explain some of the discrepancies, it doesn't explain all of them. I've still seen meaningful differences between sensors on the same vehicle at a fixed altitude.
Also, explaining the difference is altitude doesn't really fix the problem. It's still a problem many people have to account for if they want accurate readings. I don't understand why people are so reluctant to check tire pressures manually. It takes almost no time or effort.
I think doing both is better than doing either of them individually.
If only doing one, using a high quality pressure gauge is probably more precise,
as long as you fly into the pits at full speed, and your assistant quickly checks all four tires while they're hot.

geraldjust 01-13-2022 02:49 AM
Quote:
Originally Posted by timurrrr (Post 3496283)
This is a great pointer!
We would all really appreciate it if you could just share the exact request / response protocol.
I'm going to add it to my GitHub anyways, but you can just save everyone some time :)

I promise to read more into the details of how Multi-Frame Messages work!
I find "learn by studying an example" to be more effective than
"learn by first solving a puzzle that requires you to already know what you want to learn to solve it".

Also curious if you've confirmed if the same message format is working on the 2022 cars.



Totally. I definitely wouldn't rely solely on them, but they should give you a ballpark trend how much your tires gained in PSI since the start of the session.



Interesting data!



I have seen two different sensors at the exact same ambient conditions reading 2–3 psi off each other,
even though the same pressure gauge measured the same pressure from both tires.
So "0.5 psi resolution" doesn't necessarily mean "0.5 psi precision".
But again, as long as you can see the general trend...



This is perhaps even more interesting to log!

Interesting thing to find about two tires being at different temps / pressures but same ambient temp. it was a conundrum that only happen at daytime but not at night. i ended up finding out with this that a parked car whos tires face the sun warm up so much it can use a super noticeable difference in PSI. by resolution i mean yes by .5. but so far ive tested with a backup manual check of my in the valve stem and for me they been all accurate with 1psi. But i do have the oem sensors. im not 100% sure if the accuracy is maintained if using aftermarket sensor though as its just a added variable in accuracy.

also for what use is for simplicity. not saying you should rely on the sensors. but knowing the temp and psi help out a ton. i even did some measurements when heating the front tires when braking repeatedly with heavy breaking. Looking at the sensors and sure enough you can see the difference.

let me dig up the code and and il ask my business partner if i can release the info!

timurrrr 01-30-2022 03:31 AM
I FIGURED IT OUT!

To read tire pressures

Request 1:
Quote:
ID: 0x750
Data: 2A 02 21 30 55 55 55 55
Provides a response:

Quote:
ID: 0x758
Data: 2A 10 07 61 30 XX YY ZZ
The highlighted "1" means that this is the first frame of a multi-frame response.

To get the second frame, we need to send a "Continue to send request":

Quote:
ID: 0x750
Data: 2A 30 00 05 55 55 55 55
Which provides the second frame of the response:
Quote:
ID: 0x758
Data: 2A 21 WW 00 00 00 00 00
The XX, YY, ZZ and WW bytes in the response will contain the tire pressures for sensors #1, 2, 3 and 4.
I believe the encoding is:
Quote:
pressure_in_kPa(x) = (2 * x) - 100
pressure_in_psi(x) = (0.29 * x) - 14.5
where "x" is the value of XX, YY, ZZ or WW.

However it's worth noting that ScanGauge seems to use a different formula:
Quote:
pressure_in_psi(x) = (0.2977 * x) - 14.7
Given that the car is Japanese (metric), the "(2 * x) - 100" seems like a simpler / more plausible encoding than what ScanGauge uses.

To read tire temperatures
Similar thing, just slightly different bytes:
Quote:
0x750 | 2A 02 21 16 55 55 55 55
0x758 | 2A 10 07 61 16 XX YY ZZ
0x750 | 2A 30 00 05 55 55 55 55
0x758 | 2A 21 WW 00 00 00 00 00
and formulas:
Quote:
temperature_in_C(x) = x - 40
temperature_in_F(x) = (x * 1.8) - 40
Enjoy!

Thanks so much @BRZyJ for letting me play with his ScanGauge!

geraldjust 01-30-2022 03:53 AM
Quote:
Originally Posted by timurrrr (Post 3500944)
I FIGURED IT OUT!

To read tire pressures

Request 1:


Provides a response:



The highlighted "1" means that this is the first frame of a multi-frame response.

To get the second frame, we need to send a "Continue to send request":



Which provides the second frame of the response:


The XX, YY, ZZ and WW bytes in the response will contain the tire pressures for sensors #1, 2, 3 and 4.
I believe the encoding is:

where "x" is the value of XX, YY, ZZ or WW.

However it's worth noting that ScanGauge seems to use a different formula:


Given that the car is Japanese (metric), the "(2 * x) - 100" seems like a simpler / more plausible encoding than what ScanGauge uses.

To read tire temperatures
Similar thing, just slightly different bytes:


and formulas:


Enjoy!

Thanks so much @BRZyJ for letting me play with his ScanGauge!
hey you gut it! congrats! for PSI its: (X+32)/4

And to get relative pressure then :(X+32)/4 - 14.5

so you understand how extended frames work! :)

22R 01-30-2022 04:36 PM
Quote:
Originally Posted by NoHaveMSG (Post 3496118)
I really do not need this but Dayum that it too neat. I have a Scangauge II but this is the shizzle. Ima put it on my wishlist.
Nice Website and equipment.

22R

timurrrr 06-04-2022 09:11 PM
Quote:
Originally Posted by geraldjust (Post 3500945)
And to get relative pressure then: (X+32)/4 - 14.5
Looks like Autel is using ((X * 0.25) - 7.5) for psi,
which maps to ((X * 1.724) - 51.7) for kPa.

timurrrr 06-01-2024 07:49 PM
2024 update:
  1. Note that XX / YY / ZZ / WW values in the examples above are ordered by sensor index.
    That means that as you rotate tires the corners will unfortunately get reshuffled in data.
  2. gen2 cars support the exact same 0x750/0x758 protocol as the one I documented for gen1 cars.
  3. Additionally, you can passively observe tire pressure data from gen2 cars via 0x6E2:
    https://github.com/timurrrr/ft86/blo...-id-0x6e2-1762
    Good news: the data seems to be ordered by tire position, so the channels shouldn't get reshuffled if you rotate tires.
    As 0x6E2 is broadcast on the CAN bus, you can listen to that data passively, which is important when data logging using the popular RaceChrono / OBDLink MX+ combo.
    Meh news: the data uses only psi precision, unlike 0x758 which uses 0.25 psi precision.

    Thanks to @geraldjust for pointers on 0x6E2!

Luns 01-26-2026 05:32 PM
Quote:
Originally Posted by geraldjust (Post 3500945)
hey you gut it! congrats! for PSI its: (X+32)/4

And to get relative pressure then :(X+32)/4 - 14.5
I poked around a little with TPMS in Techstream. The gauge pressure values I saw would always end in 0.15, 0.4, 0.65 or 0.9.

Totally a moot point, but I think changing the 14.5 to 14.6 would align things with Techstream. It puzzles me though that it's not 14.7 instead.

This was on my gen1, over a range of pressures from 28 to 36PSI, and temperatures from 58-64F. I don't know if the fractional parts may vary outside this window. Pressures didn't exactly match my pressure gauge, but I have more faith in the TPMS sensors than my gauge.


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