Now that temperatures are dropping to freezing in the northern hemisphere, check your tire pressures. The air gets denser and I've found I lose about 5 psi, which hurts fuel economy. (I keep a nice little Black & Decker inflator in the back) I'll check tonight before I commute home, then in late January or so when the temps have dropped close to 0°F. (-18°C)
In which case, the TPMS will trigger whenever the pressure falls around 5PSI under what the pressure was when they were last set, which could be anything. You might want to set it to a known pressure
When the system is first initialised (or last initialised), the TPMS sets the trigger threshold to around 5 PSI below whatever the pressure sensors are reading. It could have been set at any time by anyone re-initialising it in the car's settings menu after that first ime, and it should be done if you've ever had the car serviced and the pressures have been adjusted (but many dealerships will not bother). There is no way to know if you've never done it yourself. My point is... as you've never done this yourself, you have no idea at all what pressure they're set to trigger at. It could be set to something sensible, but what if it's set to trigger at 1PSI or something dangerously low? In general, if you're comfortable with the pressure they're at now (e.g. 40 or so) just go into the settings menu and initialise the TPMS. Takes two seconds. If it drops to 35PSI it'll then warn you, and I'd imagine that'll be when you'd want to add some air anyway.
whenever i check the pressures, they are in the high 30's to low 40's. i would prefer there were no tpms, but that's just me.
