[funky800]

So finally my Chalk 718 Boxster arrived and i love it. Definitely the best car i have ever owned hands down.. however i already have an issue and i am hoping its something i can get fixed easily.

I was driving on the freeway and all of a sudden my tire sensor on front right was saying -4! PSI of course i panicked and pulled over as soon as i could... to get out and expect to find a flat. instead i found a perfectly inflated tire. Relieved it was an error I carried on and it reset itself - only to return - in one 200 mile round trip it alerted dangerously low PSI alot so is clearly faulty.

i have found others on the net with same problem - anyone on here had this happen?

 

[ZuffenHouseRules]

Those readings are relative to recommended pressure of course, so -4 is not necessarily visibly low. Check it with a good tire gauge.

Are you refilling the tire in between those low alerts? If so you likely do have a slow leak (maybe even a nail in the tire). That was the case for myself and another forum member, we both initially questioned the TPMS readings only to discover nails.

If you're not refilling, a gauge shows normal pressure, and still the TPMS alert intermittently goes off, then yes a TPMS issue. But I don't recall having seen that ever documented here in a little over a year...

 

[funky800]

Thanks for that @ZuffenHouseRules so no i have not put any air in yet or tested with a gauge - I simply pushed the rim to feel the firmness of the tire ( as i was on the freeway ) then i will notice that the sensor will read - 28 then back to 30 then back to 28 then to -4 then back to 30 then back to -6

so i assumed that it was faulty as it did not continue to go down...

Also i was going to ask if the -6 meant a flat or -6 PSI below recommended reading. so that answers that.

i read on another post/forum that this was seen before and that it was due to heat - i do live in socal so it was a hot day.

My car had 500 miles on at time of first error and only has 700 miles on it now

 

[ZuffenHouseRules]

Well a faulty TPMS monitor/sender replacement unit is a whole lot less expensive than a new tire so I'm glad that's all it seems to be (I'm skeptical of it being due to heat, effecting just one tire).

Myself I made the mistake of shooting a little fix-a-flat in there, forgetting that would require the tire to be replaced even if the nail-hole could have been safely plugged.

 

[grasmere]

Pics please of your chalk 718 ;-)

 

[funky800]

Ha @grasmere i have yet to take some good ones and introduce myself but its definitely on my list of things to do!

 

[autobahn]

it may actually be low. The car adjusts the pressure it "expects" for conditions, is my understanding. So add a couple pounds and see what it says.

28/30 are definitely going to trip the TPMS, you should inflate to 32-33 PSI cold and see what it says.

 

[Viffermike]

I've found that the TPMS will go off if:

- The difference in tire pressure between any of the four tires is 4 PSI or greater if any tire is below 30 PSI (This does not happen when all four tires are at 30 PSI or above -- at least it hasn't for me)
- The tire pressure dips below 25 PSI on any tire

On occasion, if the ambient temps drastically change overnight, I'll be 4 PSI off on a tire and the TPMS will go off. A minute or two of driving warms and equalizes the tires up enough to where the readings equalize and the TPMS warning goes away.

(Reference: Right now I drive with 31F/34R cold pressures. Those'll go down 1-2 PSI as we get into fall and it gets cooler here.)

 

[Nithros]

Thanks for that @ZuffenHouseRules so no i have not put any air in yet or tested with a gauge - I simply pushed the rim to feel the firmness of the tire ( as i was on the freeway ) then i will notice that the sensor will read - 28 then back to 30 then back to 28 then to -4 then back to 30 then back to -6

so i assumed that it was faulty as it did not continue to go down...

Also i was going to ask if the -6 meant a flat or -6 PSI below recommended reading. so that answers that.

i read on another post/forum that this was seen before and that it was due to heat - i do live in socal so it was a hot day.

My car had 500 miles on at time of first error and only has 700 miles on it now

Yeah can't you configure that in the display to show actual values OR the difference between the actual vs. recommended values?

 

[Viffermike]

Yeah can't you configure that in the display to show actual values OR the difference between the actual vs. recommended values?

No, and there's three good reasons behind that:

- Different tires (brand, type) have different recommended pressures
- Drivers often prefer pressures that are different than what is recommended
- It would be a way to semi-disable TPMS by setting recommended pressures so low that the system wouldn't function properly.

Keep in mind TPMS is government-mandated in many countries. To allow the user to set the trigger parameters would defeat the system's intended purpose.

 

[funky800]

So next question is 33 or 30 for comfort.. i seriously doubt i will take this over 165mph and i live in a hot area ( socal desert ) so should i be aiming for comfort 30psi all round or 33 psi all round ? suggestions.

 

[RussellHodgson]

So next question is 33 or 30 for comfort.. i seriously doubt i will take this over 165mph and i live in a hot area ( socal desert ) so should i be aiming for comfort 30psi all round or 33 psi all round ? suggestions.

I've been running at about 30 psi all round when cold. That usually heats up to about 32-33 psi when driving.

 

[funky800]

Pics please of your chalk 718 ;-)

Here are a few @grasmere i need to take some better ones still but there she is... roofs up as it was HOT lol

 

[funky800]

So this is the timeline on my tires - is this normal or faulty... each reading is Front left, FR, Rear Right, RL - all these readings are with NO adjustment in air... i have not added any air yet.


-6 warning FL
30, 30, 33, 33
-4 warning FL
30, 30, 33, 33
32, 32, 33, 35
-4 warning FL
28, 28, 30, 30
-4 warning FL
29, 29, 32, 32


are they meant to be all over the place like that?

this is over 4 days. Today I will get them all to 30 for comfort but i am worried that the TPMS will go crazy on all the tires then.

 

[Viffermike]

-6 warning FL
30, 30, 33, 33

-4 warning FL
30, 30, 33, 33
32, 32, 33, 35

-4 warning FL
28, 28, 30, 30

-4 warning FL
29, 29, 32, 32

(Returns in group added for emphasis)
Because the warning is for the Front Left tire in all four instances, and because in all groups the displayed difference in pressure is not reflected in the individual PSI readings, I'd say you have a faulty sensor in your left front wheel. You need to visit a dealer to have it looked at.

 

[funky800]

Its booked in tomorrow morning.. lets see the outcome. Thanks guys.

 

[Nithros]

No, and there's three good reasons behind that:

- Different tires (brand, type) have different recommended pressures
- Drivers often prefer pressures that are different than what is recommended
- It would be a way to semi-disable TPMS by setting recommended pressures so low that the system wouldn't function properly.

Keep in mind TPMS is government-mandated in many countries. To allow the user to set the trigger parameters would defeat the system's intended purpose.

Note that I did not say anything about being able to set the actual values - I was saying the display can show the actual values (TPMS Display) or the difference between actual and recommended (Pressure Difference display) - page 175 in the owners manual. When he said it showed -6, I thought he may have been on the Pressure Difference display.

 

[duegatti]

The pressure difference display accounts for temperature, and is only accessible when the vehicle is stopped. Thus, the OP is confusing, but it sounds like the negative values are appearing on the "absolute", first level tire pressure screen, while driving, and I think it should be apparent that if a reading for a tire is alternating between ~30psi and "-4" psi, there's a problem with the sensor, whether or not either of the values is correct.

We both have 20" wheels, and the internet teaches us that they are easily damaged and ride harshly. If you don't mind the ride (I don't. PASM on soft 95% of the time), 33 psi should help protect the wheels.

funky800 - so your TPMS multifunction settings call for 30 or 33 psi?

 

[Rideguy]

A few weeks ago I got a -4 psi warning light. Checking the display screen, all four tires showed 29 psi, (which is the Porsche recommended pressure for 18” wheels). I manually checked the tires when I got home: all were 29 cold. No warning the next time I started the car.
Four days later, same thing over three startings. I increased pressure to 30 psi and the warning went away.
I’ve driven over a thousand miles since then with no issues. Guess I’ll just keep driving and see if the gremlin returns.

 

[funky800]

So i wanted to post my findings so that others could benefit from what i was told by my local Porsche dealer.

My tires were all low first off. However i was told a certain way to check the tires and that no one gets it right. They told me to get to the Fill Info screen ( which can only be done while stationary ) once here all my tires need to be between 0 and +2

I was told not to use a tire gauge and while filling the tires use the Fill info screen to get the correct PSI. ignore the PSI screen you are simply looking for the fill info screen to register 0 - +2 on each tire then you are good.

I was told to ignore the door label, the manual etc sounded odd but at the same time made sense.

thought i would pass that on!