In addition to the very sensible advice to purchase a good-quality dial type gauge and to monitor and correct the actual tire pressure yourself, I want to add a suggestion that seems to have escaped everyone else:
If this car has a full-size spare tire, it is possible that there is a sensor on that tire, and that this is the one giving the low pressure signal. Spare tires are rarely checked by most people, and this exact scenario is what I deduced last year with a friend’s Rav-4. When I checked the pressure in his spare, it was down to something like 12 lbs on a very cold morning. Over the 3 years since he had bought the car, the pressure apparently dropped a little bit each year, thus leading eventually to this ridiculously low pressure in his spare.
However, if it turns out that low pressure in the spare tire is the source of the OP’s problem, that does not eliminate the necessity for the OP to check his/her actual tire pressure on a regular basis. Relying on this warning light, rather than on a tire pressure gauge is…not wise.