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Discussion Starter · #1 ·
Hi,

I have a 2018 Volt LT. I am seeing reported tire pressures are totally different depending on where I check.

1. On myChevrolet app on my android phone, it says: LF/LR: 33/33 (yellow wheels) RF/RR: 37/37.
2. On mychevrolet.com website, the Vehicle Diagnostics page says: 34/34 35/35.
3. On my car dash screen, it says: 33/34 37/35 (no tire pressure warning indicator turned on).


My thought is that both the apps and website should report the same numbers as those from the in-vehicle reports.

Is that normal? What do you guys see?
 

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Hi,

I have a 2018 Volt LT. I am seeing reported tire pressures are totally different depending on where I check.

1. On myChevrolet app on my android phone, it says: LF/LR: 33/33 (yellow wheels) RF/RR: 37/37.
2. On mychevrolet.com website, the Vehicle Diagnostics page says: 34/34 35/35.
3. On my car dash screen, it says: 33/34 37/35 (no tire pressure warning indicator turned on).


My thought is that both the apps and website should report the same numbers as those from the in-vehicle reports.

Is that normal? What do you guys see?
The MyChevrolet app reports the last tire pressure reading. You would need to pull down the status screen to refresh the data. On the web site you may need to wait until the page has been refreshed. As stated in the Volt Owner's Manual, after the Volt has been parked the TPMS may not give a true reading until the Volt has been drive ~2 miles.
 
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Discussion Starter · #3 ·
The MyChevrolet app reports the last tire pressure reading. You would need to pull down the status screen to refresh the data. On the web site you may need to wait until the page has been refreshed. As stated in the Volt Owner's Manual, after the Volt has been parked the TPMS may not give a true reading until the Volt has been drive ~2 miles.
Ok, I refreshed the page and app several times. At least they are consistent that they report the same number each time, just that they don't match what in-vehicle numbers.
 

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Ok, I refreshed the page and app several times. At least they are consistent that they report the same number each time, just that they don't match what in-vehicle numbers.
When parked the Volt will automatically send vehicle status information, including tire pressure readings, to OnStar over the LTE network but probably not more than once a day. Limiting the updates that are sent over the cell network is designed to minimize data usage and conserve the Volt's 12V AGM battery in the event the Volt is left parked for days or weeks and not driven as would be the case if you left the Volt in a long term parking lot.
 

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For gosh sakes buy a little air compressor from Harbor Freight or elsewhere. Get a decent tire gage and blow them up to 40. As read on a decent tire gage. The technology of the in wheel air pressure sensor is good, but not failsafe. I check and add air as needed regularly. And most people are running 40 PSI in Volt tires. Those low pressures wear out the edges of the tires.
 

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I don't pay much attention to the precise numbers in-vehicle. Those are usually 3 to 4 psi lower than any of my several manual gauges, all of which read within about a pound of each other. I think the in-vehicle number is a general idea number designed to give a heads up to an impending problem.
 

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For gosh sakes buy a little air compressor from Harbor Freight or elsewhere. Get a decent tire gage and blow them up to 40. As read on a decent tire gage. The technology of the in wheel air pressure sensor is good, but not failsafe. I check and add air as needed regularly. And most people are running 40 PSI in Volt tires. Those low pressures wear out the edges of the tires.
I just use the 12V compressor that comes with the Volt.
 

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Given the vehicle knows itself best (within the ability of the TPMS), that is "truth." Other reports are based on data transmitted via Onstar to a server and then reported via either the web site or the app that queries that server, and the numbers vary. It appears the mychevrolet.com numbers (as with myvolt.com) come from the latest periodic Onstar report and are therefore usually out of date. The app should be getting current status (in theory) when the refresh function in it is performed. Given tire temperature can cause variations in tire pressure, a slight mismatch between the vehicle's numbers and the app numbers can be expected due to timing of the refresh, but since the source of the data (for either the app refresh or the periodic Onstar reports) is the on-vehicle number, those are real. Your (slight) variations between the app and the dash numbers looks typical.
 

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I don't pay much attention to the precise numbers in-vehicle. Those are usually 3 to 4 psi lower than any of my several manual gauges, all of which read within about a pound of each other. I think the in-vehicle number is a general idea number designed to give a heads up to an impending problem.
Normal, but that will vary sensor to sensor. The TPMS sensors are not very accurate, in that when they say "40" they may in fact be 42 or 37 or something else. But they are PRECISE, in that if it said 40 last week and it now says 35, something happened and you need to pay attention--they won't vary from whatever number they reported unless the pressure did in fact change.
 

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and what makes you think a NEW reading is taken and not just the last recorded/stored number WHEN onstar does a data request ?

best way is a tire sensor learning tool : this will trigger a reading of PSi- battery voltage and temperature.
Then check with you best PSI reading gauge.

It takes a PSI change - rotating -or external radio signal to make the newer sensors send data.
I never got to play with older units that triggered with a magnet.
 

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It takes a PSI change - rotating -or external radio signal to make the newer sensors send data.
I never got to play with older units that triggered with a magnet.
Thanks, that explains why Chevrolet states that the Volt needs to be driven for a couple of miles for the TPMS to provide an up to date and more accurate tire pressure reading.
 
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