TPMS warning light (what PSI triggers it?)
 

TPMS warning light came on for a 2024 Mazda CX-5 Preferred. Checked the tire pressures and they were 30, 30, 30, 29 whereas the door sticker says the inflation should be 34 PSI. yeah, i had not checked the pressure since i bought it last october. temperature yesterday was around 25 degrees F.

does the light come on below a certain known fixed threshold or does it vary somewhat? temperature had actually been colder than yesterday so i would have thought it would have triggered sooner.

also, is the TPMS sensor different for the ones that show tire pressure on the Mazda MyApp or console screen? the MyApp just showed that the pressure was low so i don't know if a different sensor is used to report actual pressure or they have that featured disabled in less expensive trim lines.

if the latter (same sensor is used across trim lines that report actual pressure), would the pressure be recorded by OBD II as i do have a scanner?

thanks!

The light kicks on at 28 PSI or below. A notification will pop up on your app after driving with the light showing on the guage cluster. If you fill the tires up, the light on the guage cluster should go away almost immediately and you can click the X button on the notification in the app to make it go away.

The sensor Mazda uses for the CX-5 is a direct low line type.
Brand likely varies on who they get the best deal from.
It is calibrated to the recommended pressure of the OEM tire originally installed on the vehicle.
TPMS sensors normally alarm when they go 25% below the calibrated pressure or around 9 psi below 34-36 psi on the 17' and 19" wheels.
The 28 psi Alex mentioned.
However, all that is subject to whether or not you have OEM tires, wheels, sensors.
Obviously, your 2024 should have all OEM equipment but I won't take that for granted.
Also note these sensors generally don't last much over 5 years if they go that long as the built-in battery will fail.

Strangely enough, I am on my second set of tires on my 2013 MX5 and have had all tires and service done by the same shop. All sensors, both in tire and on the car are original. I asked about replacing them when I had the new Michelins installed and they said if there was a problem down the road, they would do it for free as I've been a good customer with various cars for almost 30 years, but we might as well save the money until we need to spend it.
The 2014 CX5 uses the ABS system and tire rotation to determine if there is a pressure problem so that is usually a low maintenance problem, but I think I prefer the new system.

Actually, it's not strange at all.
Most, if not all, earlier TPMS sensors used "indirect monitoring" and did not require batteries.
They use wheel speeds, accelerometers, and driveline data to estimate the tire pressure.
Whereas the newer "direct monitoring" sensors check actual tire PSI.