Tire pressure readings

[Soolim]

PSI and temperatures on each tire. Been there since the car was delivered over 4 years ago.
View attachment 88859

Good for you, and for all Roadster owners.
Why is the new MS less than the 4 year old Roadster in terms of user interface is my gripe. Tesla knows that it is useful information, or otherwise they won't include it in Roadster. And as many has echoed the sentiment, many less expensive $30K cars have it, so why not MS.

 

[AmpedRealtor]

My Tesla has it on the center display screen.

Your Tesla is not a Model S.

 

[NigelM]

Your Tesla is not a Model S.

One of them is.

 

[AmpedRealtor]

One of them is.

I think it's funny that nobody seems to know if the Model S TPMS system can provide independent readings. Seems like if the Roadster could do it years ago, today's Model S should be able to as well.

I suspect we'll get tire pressure readings after we get a decent navigation system.

 

[NigelM]

Seems like if the Roadster could do it years ago, today's Model S should be able to as well.

That was my point; different models but the know-how is there.

 

[apacheguy]

Do the diag screens on a Model S contain TPMS info? If so, how is it presented?

 

[tkizzy]

Has anybody considered that the decision not to provide the numbers is a design decision? I think Tesla want people to have the impression that a Tesla is just this black box of awesome that you plug in to charge and it just works. Maybe seeing the daily fluctuations based on temperature would add one more kind of anxiety besides the "range" kind.

That being said, I want this data (even if as a toggle buried in the settings).

 

[apacheguy]

Has anybody considered that the decision not to provide the numbers is a design decision? I think Tesla want people to have the impression that a Tesla is just this black box of awesome that you plug in to charge and it just works. Maybe seeing the daily fluctuations based on temperature would add one more kind of anxiety besides the "range" kind.


That being said, I want this data (even if as a toggle buried in the settings).

Answer is simple IMO: provide us with a read-only access code to the diag screens. That way only folks that bother to look up the code will see the advanced stuff.

 

[tkizzy]

Answer is simple IMO: provide us with a read-only access code to the diag screens. That way only folks that bother to look up the code will see the advanced stuff.

speaking of which: is this community aware of any codes other than "007"?

 

[AmpedRealtor]

Would LOVE to know the service code...

 

[mknox]

Would LOVE to know the service code...

Yeah, then TMC would have to open up a whole new discussion forum just for the questions like "I entered this code and now my car won't run. What should I do?"

 

[FlasherZ]

I think it's funny that nobody seems to know if the Model S TPMS system can provide independent readings. Seems like if the Roadster could do it years ago, today's Model S should be able to as well.

It depends upon the supplier of the TPMS subsystem used. Tesla switched suppliers as well, so you need to consider the old one vs. the new one. I have great faith that the newer subsystem can report it, because it seems to be much smarter than the old one. It does send the specific tire location to the control/management unit. I doubt we'd see that without the capability to get the tire pressures. At that point it becomes a feature element for Tesla's software rather than an issue with subsystem capability.

In the old subsystem, I'm unsure. The threshold tire pressures for alert had to be programmed into the TPMS subsystem itself using the tool, not Tesla's code (I know because in the early days they changed the alert threshold on my car and they had to use the special TPMS tool to do it). That leaves some doubt as to whether the control unit could get those tire pressures. We also know that the TPMS module knows which sensor is on which tire in that unit, but don't know if the CANbus alert messages sends the specific alert or not.

The fact the Roadster had it doesn't necessarily mean that Model S has it. It is likely that the supplier for Model S isn't the same supplier for the Roadster. Did Tesla or Lotus provide the TPMS subsystem? (I'm no expert on what Tesla bought from Lotus - body+chassis only? or did some of the other components come too?)

 

[mknox]

In the old subsystem, I'm unsure. The threshold tire pressures for alert had to be programmed into the TPMS subsystem itself using the tool, not Tesla's code (I know because in the early days they changed the alert threshold on my car and they had to use the special TPMS tool to do it). That leaves some doubt as to whether the control unit could get those tire pressures. We also know that the TPMS module knows which sensor is on which tire in that unit, but don't know if the CANbus alert messages sends the specific alert or not.

I wonder, though, if this is two different things. My last car had individual tire pressure readouts, but it also had a red "Low Tire Pressure" symbol that would light up if one or more tires got too low. Perhaps even the early Tesla system is sending actual pressures, and then some second system is looking for one or more of the values to go high or low out of band. I can see Tesla having to re-program that parameter.

 

[apacheguy]

Yeah, then TMC would have to open up a whole new discussion forum just for the questions like "I entered this code and now my car won't run. What should I do?"

Precisely. Which is why it would be read-only. That's all I'm asking for.

 

[FlasherZ]

I wonder, though, if this is two different things. My last car had individual tire pressure readouts, but it also had a red "Low Tire Pressure" symbol that would light up if one or more tires got too low. Perhaps even the early Tesla system is sending actual pressures, and then some second system is looking for one or more of the values to go high or low out of band. I can see Tesla having to re-program that parameter.

It could be, although if the old system had the capability of directly reporting pressures, I would expect the Tesla software to take responsibility of generating the alert, rather than having the subsystem do it. It would create much more flexibility than having to make each service tech re-program the subsystem in every car When Tesla decided to change the threshold, they could have developed some simple code to move the pressure alerting to the main supervisor instead. It would save a significant amount of time in the service processes.

I don't have any specific knowledge of the module that they use, I'm just making educated guesses based on the information we do have.

 

[apacheguy]

Pretty sure the MCU generates the alert. I remember in the early days when Model S was in its infancy, one of the software updates decreased the pressure threshold because owners were being alerted too frequently.

 

[FlasherZ]

Pretty sure the MCU generates the alert. I remember in the early days when Model S was in its infancy, one of the software updates decreased the pressure threshold because owners were being alerted too frequently.

That wasn't via software update. Unfortunately, that had to be programmed into the TPMS module. That was in the days prior to the St. Louis service center, and when Leo flew out to work on my car he had to use their TPMS tool to reprogram the threshold (I watched him do it). IIRC, they changed it from 38 to 36.5, or from 38.5 to 36... one of the two.

 

[apacheguy]

Ah, I see. So would this be the same scanning tool they would use to determine which sensors are throwing errors? All I know is Tesla was able to identify two specific sensors on mine that were generating errors and only targeted those for replacement. It mentioned on my repair order that they "pulled the logs" which makes me skeptical of this explanation as it indicates the MCU does receive tire specific data from each sensor.

 

[FlasherZ]

Ah, I see. So would this be the same scanning tool they would use to determine which sensors are throwing errors? All I know is Tesla was able to identify two specific sensors on mine that were generating errors and only targeted those for replacement. It mentioned on my repair order that they "pulled the logs" which makes me skeptical of this explanation as it indicates the MCU does receive tire specific data from each sensor.

Yes, that was the tool they used.

Way back then, I also had 2 sensors bad and he had to use the scanning tool to determine which ones weren't responding. Not sure if "pulled the logs" is a general term they're using for using the scanning tool, or if they added some capabilities.

 

[Yonki]

I just read this entire thread for the first time. From what people have said (essentially "you need to drive the car around to reset the TPMS / get a new result from the TPMS"), it seems to me that the most likely explanation is that the Model S is not measuring the absolute tire pressure of each tire. If they were, I'm certain they would be displaying it (and without having to drive the car to get a new reading). Why wouldn't they?

Instead, it looks like they are using the old, inexpensive (free except for a few lines of code) "TPMS" of comparing the relative RPMs of the 4 tires using the same sensors they use for ABS and traction control. An underinflated tire has a shorter effective radius, so it has to spin faster to cover the same distance. If one tire is consistently spinning at a higher speed relative to the other 3, the car can pretty safely assume that that tire is underinflated. That is why the system won't update until you've driven the car, and how it can tell you the specific tire that has a problem.

People have talked about there being different versions of TPMS in the MS, which makes me less than 100% certain of this conclusion, but possibly they are talking about different versions of the RPM sensors used to implement TPMS, or different TPMS algorithms in the software.

If I'm right, there is no way software can add per-tire, absolute pressure TPMS.

- - - Updated - - -

I forgot to mention that I learned about this type of TPMS the hard way. 10 years ago I parked my old Mitsubishi 3000GT VR-4 Spyder (hardtop convertible - was fun while it lasted!) at a movie theater, where unbeknownst to me a punk who'd tried to steal the parking space I'd been waiting for had put a pebble inside my valve stem then put the cap back on loosely, letting the air leak out of the tire over the next two hours. When the movie was over it was dark, so I got in the car and drove away. A minute later, on the highway doing 65, my tire pressure monitor went off. I pulled off at a gas station and saw that my right front tire was totally flat and I'd been riding on the rim (I'd noticed the car felt a little off as I left, but it wasn't that much, probably because my low-profile tires were already like riding on the rim). Since this was a mechanically-coupled AWD car I had to replace all 4 tires.

So that movie (and if I recall it wasn't even very good) cost me $800 and taught me that no parking space is worth fighting for no matter how late you are...

If I'd had the TPMS my current Acura has I would have known before I moved the car out of park.