Its Tire Pressure Season – Again

Well, its November and time again to speak about the Tire Pressure Monitoring System (TPMS), and its associated warning light. We do this every year, but every year several million more drivers who have recently replaced their cars will encounter the light for the first time.

Rare Tire Pressure Light w/ArrowsTire Pressure Monitor SymbolThese are two versions of the TPMS light, and either one is easily the most misunderstood warning light you’ll find on your instrument panel.


First, unlike other amber lights, there is nothing wrong with your car — it presents you information about your tires and likely as not there’s nothing actually wrong with them either.

There are two possible reasons why you are seeing this light. First, as the weather cools the most likely possibility is that all four of your tires are low on air. The second possibility is that one tire has a leak of some sort, but we’ll return to that in a moment.

Air expands when heated and contracts when cooled. Air that has cooled and contracted in your tires leads to reduced tire pressure. The warning light comes on and air needs to be added to your tires. Its important to note that air has not actually leaked out.

But the warning light does not discriminate between cooling air and actual air leaks. It comes on if one tire is low or all four is low, so more information TPMS displayis needed. Your model may or may not include a display option like the one shown. It is a read out of the tire pressure in the individual tires. If all four tires read roughly the same, within a pound or two, the warning light is the result of seasonal cooling.

If one tire is several pounds lower than the others, 5, 6 or 7 pounds or more, that tire is leaking and needs to be serviced as soon as possible.

Some vehicles feature only the warning light. In this case, the tire pressures need to be checked by hand to determine the cause — a single leak or seasonal reduction in all four.

If you’re not comfortable checking your tire pressures or with filling them, the good news is that pretty much every tire store, repair shop or dealer will fill them for you at no cost. Its simple for them to do and they make a friend in the process, meaning more business from you down the road. Please drop in on one of them.

If you are comfortable with checking your tire pressures and adding air, by all means do so. But you will first need to know the required tire pressure. Tire pressure labelLook for a label just below where the driver’s door latches. The required pressures will be shown. They will match left to right but will likely be a little different front to rear. Set the pressure on the pump and trust it. It will stop pumping once the proper pressure is reached. You may also find yourself using a pump with a built in gauge. Trust it as well and be sure to add your spare tire to the routine.

Each tire valve has a cap that needs to be unscrewed and removed. Don’t lose it — it keeps water and dirt out and will keep the valve from developing a leak.

And one final thought, and its for manufacturers. Every vehicle equipped with the tire pressure warning light simply must be equipped with this display. Leaving your customers in the dark when this light comes on is unacceptable to us.

Check out the video below and safe travels everyone.


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