Steering angle: 0 degrees
LF wheel speed: 305 rpm
RF wheel speed: 293 rpm
LR wheel speed: 302 rpm
RR wheel speed: 285 rpm
In this case, it may be possible for the car to determine that you probably have some incorrect pressures, but it may not know exactly which tire(s) is/are wrong. Nor does it know what the pressures are.
It also perfectly calculates distance to empty in miles/kilometers.
2021-2023: https://parts.ford.com/shop/en/us/electrical/other-electrica...
2015-2020: https://parts.ford.com/shop/en/us/electrical/other-electrica...
2013-2014: https://parts.ford.com/shop/en/us/electrical/other-electrica...
In fact, your example looks more like one overinflated (or perhaps overheated) tire --- RR.
You still don’t know for sure that it needs inflated, because:
1. setting tire pressures incorrectly is not uncommon
2. That button is user accessible and might be pressed inadvertently or by someone who didn’t set the tires correctly
3. If all tires change in pressure at the same time, it would be undetectable
This is why these systems generally tell you to “check” your tires, rather than inflate a specific one. If they made that assumption, your car could be telling you to inflate an already overinflated tire.
There are many cars with tpms in the wheel that still won’t tell you what wheel it is or what’s the pressure, so I still much rather have no sensor to deal with trading the “inconvenience” of checking the tires once the light comes on, which is what you would do anyway.
I was explaining why the engineering of the system dictates the information that the interface provides.
I don’t care what pressures the tires have as long as they are good. If I stop to inflate one, I check all of them anyway, with a real gauge. But that’s just me, I know.
The transponder in each tire just shouts out its serial number and pressure on 315mhz and then sleeps for a random amount of time. The car counts how many times it has heard the various serial numbers, and assumes the top four most frequently heard serial numbers are its own tires (as opposed to those on the car next to it).
It is sort of stupidly easy to gather location data from TPMS sensors. If I ran a major criminal gang I'd track the cop cars this way. 315mhz is almost VHF, it goes a long way. One receiver per city block should do it. Covering your turf would be easy.
Other vehicles actually know which is which without being told. I'm not sure exactly how this is done, but I'm guessing/vaguely recall hearing they do this by using multiple receivers.
As for tracking from a distance - these sensors have very low output power, and a lot of their signal is blocked by the metal wheel. It can somewhat be done but you'll need more than one receiver per block if you want 100% coverage.
Sources: worked as a tire shop technician for a while, messed around with SDR, read a lot online. Also: https://web.wpi.edu/Pubs/E-project/Available/E-project-09111...
That's one of the revelations from Snowden files. Us govt does this!
It's always been this way.
I understand having idiot lights for idiots, and sure, do that on the dash, but please give end users any way to get some actual info. It’s the “door ajar” when the vehicle knows which door but doesn’t disambiguate to the user. It’s bad design, or malicious design to boost dealer profits.