Some time ago, carmakers and the government concluded that all new cars coming off the line should be equipped with low tire pressure indicators on the dash. Don't ask me why they decided this indicator should look like you just got three points in a game of horseshoes rather than just a picture of, I don't know, A TIRE! But, they did. The amount of confusion this creates is stupefying. Some manufacturers now include more helpful notes like "low tire" or diagrams of a tire on the vehicle. But for so many of the more economically priced cars, you got the horseshoe.
A number of customers come in with this on and say, "Don't sweat looking at that, it's been on forever" (!) I wouldn't want this thing malfunctioning when I'm somewhere between here and there. If you drive on a tire that's flat, even for a short time, you'll inevitably ruin it. If you have an all-wheel drive vehicle, go ahead and budget $800 for four new tires. Now that $300 repair doesn't sound so bad. This has been mentioned in other articles, so I won't bore you with any more reprimands.
Here is the thing to understand about TPMS (Tire Pressure Monitoring System) lights. There are two light states: blinking and solid. When the light is on solid, you have a low tire somewhere. When it blinks, you have a malfunction in the system. Diagnosing the blinking light isn't rocket science, but it does take a special tool to both locate the source of the problem and test. This tool is also needed when rebooting the system, replacing the sensor and often, turning the light off. If the light is blinking, there aren't a lot of choices, it needs to go to a shop to be diagnosed. The repair for this can be a couple of hundred dollars, if a single sensor is to blame, up to well over a thousand if all four sensors and/or the module needs replacement. That said, this is fairly uncommon. More often than not, we replace a sensor or two and the car is off and running.
At the onset of winter our phone always starts ringing like crazy with people who have this light on. As the weather gets chilly, the air pressure in the tire drops and sets the light off. In the fall, when customers come in for service, we typically like to set tires a little higher so that this doesn't occur. But, if the last time we saw your vehicle was in May, it's inevitable, the light will come on. If you are someone who likes to air their own tires (are you crazy, by the way, why pay when any good shop will do it for you for free?!), make sure to use the placard on the driver side door panel to find cold and warm weather temperature recommended pressures. Not every tire is 32 PSI! But, keep in mind car makers aren't putting pressures on there to achieve the best fuel economy, they want you to have a comfy ride which comes at the expense of MPG. I always go a little high for this reason. I don't care that much if my ass hurts because I feel more of the bumps in the road. That's just me.
But, if the light is on, don't ignore it. It's helpful and might save your skin some day.