What is the Horseshoe-shaped Dashboard Warning Light?
Its cold weather time again and time again to speak about the Tire Pressure Monitoring System (TPMS), and its associated warning light(s). Every year several million more drivers who have recently upgraded their cars will encounter the light for the first time.
These are two versions of the TPMS light, and either one is easily the most misunderstood warning light you’ll find on your instrument panel. And the fact that its shaped like a horseshoe doesn’t help.
First, unlike other yellow/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.
Why the Light Is On
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 (and/or the spare!). 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 is 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.
And while on the subject, a thought for manufacturers. Every vehicle equipped with the tire pressure warning light simply must be equipped with this display. Leaving your customers in the dark by displaying the warning light only is unacceptable to us.
Now, 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.
If your vehicle is one that features only the warning light, 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 car 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. Look 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.
Learn more about this warning symbol here.
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Remember that only proper service and repair procedures will ensure the safe and reliable operation of your car. In addition, proper safety procedures and precautions, such as the use of safety goggles, the right tools and the equipment should be followed at all times to eliminate the possibility of personal injury or improper service which could damage the vehicle or compromise its safety.
These posts are for information sharing purposes only, and should not be used in lieu of an OEM service manual or factory authorized service procedure. We are not in the auto repair business nor do we publish automotive service manuals. Nothing we include on these pages and posts has been reviewed, approved or authorized by any vehicle manufacturer.
Technology is always changing and what is current and accurate today may be literally out-of-date and inaccurate tomorrow. And when it comes to the current state of flux in the auto industry, nothing is more true.
The author has 25 years of automotive experience and has assembled the most extensive collection of symbols and warning lights anywhere (over 1,000!) and can help you open and start any keyless start car with a dead key fob battery. BA, St. Joseph’s College, ME: MS, Rensselaer Polytechnic Institute, NY
A word on tire pressure and tire pressure gauges
So its that time again. Time when the weather cools and your tire pressure drops, as directed by nature, and you’ll soon see the Tire Pressure Monitor System (TPMS) light. The one that looks too much like a horseshoe.
Set the pressure, 36 lbs in the case of the EV, inflate the tire and the pump stops and beeps when it reaches the the pressure that’s been set. I then check the accuracy of the pump with my pencil type pressure gauge. It read 34 lbs on each tire.
Now one might think that powered system like the pump I used might be more accurate, but this is clearly not the case. And while I do recognize that 34 lbs is quite literally close enough, getting to 36 lbs will stave off the next need to fill again as the temperature continues to drop by a few degrees.
And of course, 2 days later its 60° and all 4 tires are at 36 lbs…
Keep it simple and stay with the mechanical gauge and its easy to carry. And do back-up the pump and check what’s actually gone in to your tires.
For more tire pressure, check our TPMS page.
——————————————————————-
Remember that only proper service and repair procedures will ensure the safe and reliable operation of your car. In addition, proper safety procedures and precautions, such as the use of safety goggles, the right tools and the equipment should be followed at all times to eliminate the possibility of personal injury or improper service which could damage the vehicle or compromise its safety.
These posts are for information sharing purposes only, and should not be used in lieu of an OEM service manual or factory authorized service procedure. We are not in the auto repair business nor do we publish automotive service manuals. Nothing we include on these pages and posts has been reviewed, approved or authorized by any vehicle manufacturer.
Technology is always changing and what is current and accurate today may be literally out-of-date and inaccurate tomorrow. And when it comes to the current state of flux in the auto industry, nothing is more true.
The author has 25 years of automotive experience and has assembled the most extensive collection of symbols and warning lights anywhere (over 1,000!) and can help you open and start any keyless start car with a dead key fob battery. BA, St. Joseph’s College, ME: MS, Rensselaer Polytechnic Institute, NY