Model 3 TPMS sensors are junk

[dhanson865]

What's your source that the manufacturer recommended tire pressure is based on "coldest temperatures you will encounter"?

Anyone who has been driving for any length of time (I've been driving for 30+ years) knows that PSI is affected by temperature. I routinely adjust inflation levels on all of my vehicles in the fall when night-time temperatures start to dip close to freezing.

The issue here is not an ignorant owner as you've implied. The issue is that Tesla has provided an incredibly narrow margin in PSI range before the sensors alarm. That is proven with photos of tires that are within 2-3 PSI of Tesla's recommended tire pressure level still alarming. That is ridiculous and Tesla needs to fix it but good luck getting them to even acknowledge that it is an issue.

As big or bigger problem is Tesla not accounting for atmospheric pressure differences at altitude which forces those of us who live at higher altitudes to over-inflate the tires to prevent them from alarming in the first place.

How you and other people don't get this part is a mystery to me.

You routinely do so but you avoid specifying temps with your PSI. All I'm asking for is for you to specify PSI @ temperature @ altitude instead of just PSI @ altitude. It's a simple documentation step that should be followed for any discussion about TPMS errors.

I am not refuting that there is an altitude factor, I am asking for you do document the issue properly.

 

[UngaBunga1989]

I'll take a picture next time I drive it since I haven't gone out to freeze my nuts off and top them up more. I was driving back and all tires were reading 40 or 41 psi and 3 of the 4 were in alarm.

Being an engineer this is the kind of thing that will really put my knickers in a twist. Not everyone lives in SoCal where they consider 60 a cold snap.

Why bother getting worked up over it? You have a service appointment scheduled. Ask them to fix it and enjoy the car. It's just one of life's curveballs. Sorry it is so cold where you are! This weather has been insane...

 

[voip-ninja]

Why bother getting worked up over it? You have a service appointment scheduled. Ask them to fix it and enjoy the car. It's just one of life's curveballs. Sorry it is so cold where you are! This weather has been insane...

Yes I am also an engineer and it's irritating not only to deal with the issue but to know that the fix, or at least cheap workaround of a larger PSI margin, is trivial.

 

[voip-ninja]

Why bother getting worked up over it? You have a service appointment scheduled. Ask them to fix it and enjoy the car. It's just one of life's curveballs. Sorry it is so cold where you are! This weather has been insane...

This has less to do with temperature and more to do with altitude. Which I've only stated about 100 times in this thread.

I do not have a service appointment and since my local service center has a 5 day back log (check the car in and it's about 5 days sitting in their lot before a tech even looks at it) I won't be bringing it in for this problem, there's nothing they can do about it anyway. The only "fix" will have to come from the software developers in CA.

 

[SomeJoe7777]

@voip-ninja is correct in that the main problem here is the warning/alarm setpoint in the Tesla.

Federal law requires a TPMS warning system in all light vehicles capable of detecting when one or more of the vehicle's tires is 25% or more below the manufacturer's recommended cold inflation pressue. This is federal law 49 CFR Part 571-585.

The minimum warning setpoint on a Tesla Model 3 that would be in compliance with the law would be the recommended placard pressure minus 25% = 42 psi - (42 psi * 0.25) = 31.5 psi.

It appears the warning setpoint is actually set to around 37.5 to 38 psi. This appears to be 25% below the maximum inflation pressure (50 psi) rather than the recommended pressure. In my opinion, Tesla did one of the following:

1. Inadvertently calculated the setpoint incorrectly by using the maximum inflation pressure rather than the recommended pressure.
2. Assumed that an owner may wish to inflate his tires to the maximum inflation pressure for range considerations, and designed the warning setpoint to be 25% below that. This would still be in compliance with the law.

Either way, the current warning setpoint is only 4 psi below the recommended inflation pressure. This leaves a margin of only 40 degrees F between properly inflated and the alarm setpoint, or a margin of 8000 feet of altitude between properly inflated and the alarm setpoint. The margins for each are even less when the two are combined.

The problem due to temperature can be worked around with diligent attention to the cold inflation pressure, although that's not ideal.

The problem due to altitude is more severe because it can't be worked around. Indeed, if you live at or above 8,000 feet elevation, there is actually no inflation pressure that would meet the placard recommendation without tripping the low pressure alarm, regardless of temperature.

This is a design problem that Tesla should address. There are several solutions, but the simplest would be to lower the alarm setpoint to 31.5 psi. This is fully in compliance with the law and would remove all spurious alarms due to temperature and altitude.

 

[Knightshade]

It appears the warning setpoint is actually set to around 37.5 to 38 psi. .

then why are folks having TPMS warning at 39-40 psi at ~sea level?

 

[rlb4]

I don't get a warning until 37 psi. My elevation is about 100 ft.

 

[Knightshade]

I don't get a warning until 37 psi. My elevation is about 100 ft.

Post #92 is a pic of someone getting it (on all 4 wheels) at 40 psi.

I've personally gotten it at both 39 and 40- and sometimes only one 1 or 2 wheels (and sometimes all of em) even when they were all at that PSI.

Plenty of stories from owners in similar situations to both.

So there's clearly something going on other than "trigger if the PSI is below X"- and that something is kinda crap.

 

[TeeEmCee]

Post #92 is a pic of someone getting it (on all 4 wheels) at 40 psi.

I've personally gotten it at both 39 and 40- and sometimes only one 1 or 2 wheels (and sometimes all of em) ...

This post sounds really dirty!

 

[rlb4]

Post #92 is a pic of someone getting it (on all 4 wheels) at 40 psi.

I've personally gotten it at both 39 and 40- and sometimes only one 1 or 2 wheels (and sometimes all of em) even when they were all at that PSI.

Plenty of stories from owners in similar situations to both.

So there's clearly something going on other than "trigger if the PSI is below X"- and that something is kinda crap.

I just stated that my sensors seem to work normally. I agree SOMETHING is going on. That something is that the sensors are junk, for a lot of people. The sensors should alert at a predetermined psi, a reasonable amount below the recommended psi. The programmers really need to fix the problem. Luckily mine seem to be working ok.

 

[mongo]

Post #92 is a pic of someone getting it (on all 4 wheels) at 40 psi.

I've personally gotten it at both 39 and 40- and sometimes only one 1 or 2 wheels (and sometimes all of em) even when they were all at that PSI.

Plenty of stories from owners in similar situations to both.

So there's clearly something going on other than "trigger if the PSI is below X"- and that something is kinda crap.

General comment regarding pictures of warnings: the reset function may not engage instantly and/or may have hysteresis. Due to that, if it goes past the low trip point, but then moves back to the good range, it may not reset immediately. Especially if they have a filter or higher reset points made up numbers: error at 37 clear at 42psi or 30 minutes at 40psi.

Lame anecdote: Our old Buick always threw one additional low pressure warning after the tire was fixed..

 

[Knightshade]

General comment regarding pictures of warnings: the reset function may not engage instantly and/or may have hysteresis. Due to that, if it goes past the low trip point, but then moves back to the good range, it may not reset immediately. Especially if they have a filter or higher reset points made up numbers: error at 37 clear at 42psi or 30 minutes at 40psi.

Lame anecdote: Our old Buick always threw one additional low pressure warning after the tire was fixed..

Generally I've had it happen very first thing in the morning on starting the vehicle when it's especially cold out, and it stays on beyond 30 minutes.

Now, it gets that cold rarely enough here it's only happened a few times, hence why it's tough for me to figure out WTF it's using to determine if a tire is actually low or not (especially when it's warning for only a couple of tires even when showing them all the same pressure on the display) but it's pretty bizarre when it happens.

 

[mongo]

Generally I've had it happen very first thing in the morning on starting the vehicle when it's especially cold out, and it stays on beyond 30 minutes.

Now, it gets that cold rarely enough here it's only happened a few times, hence why it's tough for me to figure out WTF it's using to determine if a tire is actually low or not (especially when it's warning for only a couple of tires even when showing them all the same pressure on the display) but it's pretty bizarre when it happens.

Oh sure, I'm not saying exactly what Tesla's algorithm is, but on a value warning like that, it seems like they would have separate set and reset points. The sensors themselves typically transmit rarely when the tire is not spinning, every minute or so when it is, and nearly instantly on a large pressure change. Since these are the modern ones with direct pressure readings, we can see that the data has updated, but it may have dipped below the threshold on a couple tires at some point in the night.

 

[voip-ninja]

In alarm again today.

 

[gilscales]

Not everyone lives in SoCal where they consider 60 a cold snap.

WELL!, I'll have you know that when traveling to an overpriced restaurant just the other day my extremely expensive Napa wine that was in the trunk dropped a few degree's below ideal serving temperature here and my trophy wife had to wait an extra TEN MINUTES! for the wine to warm up satisfactorily, Talk about a cold snap!

Then, to top it all off, I pulled up to another Tesla and they refused to pass me the Grey Poupon!

 

[JohnBinSC]

How much the outside air pressure affects the load carrying ability and the contact patch shape of the tire versus the pressure exerted on the tire by the vehicle itself.

Hi GregD60,
i wondered the same thing, but after thinking about it for a minute, i concluded that it is indeed the differential pressure between the tire and the ambient atmosphere that determines the net outward pressure (force per unit area) on the tire due to inflation, and thus the amount of deflection of the tire under the additional load of the weight of the car. Even though the tire is resting on the ground, the ambient pressure is always pushing back in on all parts of the tire balancing out the internal pressure. There may be some subtle edge effects where the force vectors don't exactly align, but I expect the simplest calculation would be: contact patch area = weight / differential pressure. If you use lbs for weight and psig for differential pressure you would get the contact patch area in square inches. i would bet that is within 10% or better of any more sophisticated calculation using a physical model of the tire etc.

So yes I agree with the concensus here that Tesla should implement a GPS altitude based adjustment to the TPMS reading. I
I also would like there to be button to acknowledge the tire pressure warning with an option to indicate that you are intentionally running the tires a bit lower (or higher) than spec pressure.

I am here because i just started getting a TPMS warning on one wheel of my M3 while it is still indicating it has a pressure of 41 psi.
In my case, I think the problem is related to the recent upgrade to software 2019.5.2. I never had the problem before. Some other related behavior is that the TPMS is reporting "--" for all 4 wheels when I get into the car in the morning now. I never saw a reading on "--" before this in 10.7k miles/7 months.

 

[GregD60]

LOL good luck.

It's not a problem for most people and nobody for who it is a problem has any influence.

Someone proved to the Broadway service center in CO that this problem existed and simply got refuted that most of the gauges used to measure tire pressure aren't accurate.

I had my car in for service at the Broadway service center last week, and their attitude has changed regarding the inflation pressures. The service adviser acknowledged the problem, said that Tesla engineering knew about it, but he didn't know when or how they were going to fix it. I asked him what pressure he'd recommend to set the tires to in the meantime. He said that they inflate the tires to 45 PSI at the service center to avoid the low tire pressure messages, but that it was up to me what I wanted to set the tire pressures to on my car.

 

[ngogas]

At least you all know it is working. Just a bit too sensitive. Lol

 

[Ludalicious]

View attachment 378656 View attachment 378649 View attachment 378650 In alarm again today.

Have had lots of issues with my stock sensors. I eventually just pulled them all out and went with an aftermarket one. Haven't had any issues since.

 

[vickh]

overinflation a short term solution? rough ride?

I used to by like 5PSI like hypermilers suggested. Does it give better range like with ICE ?