Diagnostics say my tire pressure is low. How accurate is the TPMS?

[wahoowad]

Just took delivery of my 2019 Trail Boss this past Saturday, and the sales guy showed me how the Tire Pressure Monitoring System shows up in the infotainment screen. When he showed it to me it said tires were 36 to 37 psi, which I assume was the correct pressure. But now I am looking at the online vehicle diagnostics and it says they are in fact low and it recommends 41 psi.

 

Just curious how accurate this Tire Pressure Monitoring System is, and if the diagnostics are accurate as of today? Online it says "Diagnostics Report Date: 11/16/19" which was 2 days ago so is this even a real time system?

[davester]

It's real time in the truck (what's displayed on the dash).  RTFM or the door jam for what pressure to run your tires.  Door jam typically lists the max pressure, which is needed for a fully loaded truck.  Running around empty, a lower pressure typically gives a better ride, the manual should have the range.

 

Never assume the dealership bothered to actually check anything to prepare your vehicle.  Check every fluid, grease nipple, tire pressure and lug nut that it's right.

[greco2003]

You can refresh the diagnostics in the app. The TPMS sensors are within 1-3lbs accurate.

[Dnt]

When I picked up my new Denali Ultimate ($68,535.00 MSRP) the salesman had me push the onstar button to set that up and I also updated the GM phone app.  The first thing that popped up on the phone app was that all four tires were yellow flagged for low tire pressure. The salesman drove it over to service and they aired up the tires. Next day is when I realized the heated steering wheel did not work, I guess that is about average for most dealers and their vehicle prep.........maybe if the sticker were over 100k they would do better Hahahaha       

[redwngr]

Door post label will have the correct pressures for fully loaded truck -- and with the tire size installed when assembled.  Different tire size can mean different recommended pressure -- which is why the tire sticker is printed for each truck.

 

The programming for the TPMS display can be changed ater it leaves the factory (but probably isn't).

 

If it's changed the Onstar app will list the revised TPMS settings as 'recommended'.  

 

 

While you're in the business of checking the TPMS, check the door post label and verify the recommended numbers in the onstar app are the same.