Solid light versus flashing light
A steady TPMS light means at least one tyre is low. A light that flashes for about a minute at startup then stays solid means the system itself has a fault — usually a failed sensor rather than a pressure problem. The distinction saves a lot of guessing.
Sensor batteries are not replaceable
TPMS sensor batteries are sealed into the sensor. When one dies the sensor is replaced, and the new one has to be programmed and relearned to the vehicle. That relearn procedure differs by manufacturer, which is why a tyre shop that does not have the right tool sometimes leaves the light on.
Cold mornings set it off
Pressure falls with temperature. A car that was fine in September can trip the light on the first cold morning without anything being wrong. Set pressures to the placard on the driver's door jamb, not the number on the tyre sidewall.