Reading Tire Pressures Real Time via TPMS Sensors

[timurrrr]

From the manual:

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

[ermax]

Originally Posted by LimitedSlip

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]

Originally Posted by timurrrr

From the manual:



I sense some trickery in these

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]

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

[timurrrr]

Originally Posted by timurrrr

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...

[geraldjust]

Originally Posted by timurrrr

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...

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

[NoHaveMSG]

Originally Posted by geraldjust

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]

Originally Posted by NoHaveMSG

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]

Originally Posted by geraldjust

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

[Pat]

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]

Originally Posted by Pat

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]

Originally Posted by geraldjust

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]

Originally Posted by braz009

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]

Originally Posted by Pat

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.