There are a few lights you never want to see when you’re behind the wheel: flashing reds and blues in your rearview mirror, a cellphone’s glow in the backseat when you thought you were driving alone, and of course, the tire pressure sensor light on your dash.
We can’t help you with Johnny Law or the bloodthirsty lunatic who’s sharpening a machete behind you, but we can fill you in on how to deal with that pesky light on your dash.
- What Does Your Tire Pressure Sensor Do?
- When TPMS Goes Wrong — Diagnosing Problems With Your Sensors
- How Much Does it Cost to Replace a TPMS Sensor?
- How to Replace a TPMS Sensor Yourself
- Can I Drive My Car with a Faulty TPMS Sensor?
- Do I Have to Replace My TPMS Sensors Every Time I Get New Tires?
- Final Thoughts
What Does Your Tire Pressure Sensor Do?
Back in the olden days, when dinosaurs roamed the earth and computers were big enough to take up an entire room, there were only a few ways to tell if your tires had low pressure.
You could look at them, kick them, wait for a well-meaning stranger to tell you that they thought the tires looked low, or as a last resort, take out a tire pressure gauge and measure them.
That all changed with the advent of tire pressure monitoring systems (TPMS). First seen on European luxury cars in the 1980s, TPMS made its way across the pond around a decade later, when one was included on the 1997 Chevy Corvette.
A vehicle equipped with TPMS has a tire pressure sensor inside each tire. Some TPMS, especially aftermarket models, consist of sensors that screw onto the valve stem, while others are mounted to the inside of the tire’s rim.
If that tire becomes underinflated for some reason, the sensor will send a message to the car’s computer, causing it to flash an warning light or message on your dash.
This can be extremely useful, as it alerts you the problem before you have a catastrophic blowout; they’re so useful, in fact, that thanks to the TREAD Act, every car made after September 2007 has to have a TPMS installed if it wants to be sold in the United States.
When TPMS Goes Wrong — Diagnosing Problems With Your Sensors
While having a TPMS is an excellent thing for any car — after all, if Congress likes something, it has to be good, right? — that doesn’t mean they’re perfect. Like any piece of equipment, they sometimes malfunction.
Below, we’ll show you what it looks like when your TPMS starts to act up, so that you can diagnose the problem with confidence.
For the purposes of this discussion, we’ll only look at factory-installed TPMS that are mounted to the rim. If you have an aftermarket system, consult your owner’s manual for more help.
Your First Sign of Trouble: The Warning Light
If one of your tires is experiencing low pressure, your TPMS will alert you by activating a warning light somewhere near your gauges (usually right next to the speedometer). This light is designed to look like an exclamation point inside of a tire.
When you see this light come on, that’s your signal to check your tire pressure as soon as you can. You can use the handheld gauge that you keep in your glove compartment (you do keep a tire gauge in your glove compartment, right?), or you can have a pro check it at a garage or tire shop.
If it turns out that one or more of your tires is low, you should air them up to the factory specifications and reset the alarm. To do this, look for the button near the steering wheel that has a picture just like the warning light on it; hold it for a few seconds and the light should go off.
If there’s no button on your dash, you might have a car with a self-learning system. In that case, all you have to do is drive at 50 mph or more for 5 or 10 minutes and the problem will solve itself (and try not to think about what else your car is teaching itself, or why your on-board GPS is powered by SkyNet).
Sometimes, though, the light will come on even if all your tires are fine — or it will keep coming on even after you’ve filled your tires to the proper PSI. If that happens, it’s a clue there might be an issue with your TPMS.
What to Do if the Light Keeps Coming On
If you can’t get that pesky light to go away, you’ll have to talk to your car to find out where the problematic sensor is, so we hope you speak binary.
If for some reason you don’t, though, you can still ask your car what’s going on — you’ll just need an OBD2 scanner or access to the dashboard computer, depending on your make and model. Consult your manual to learn how to do either one of these things.
Failing that, disconnecting and reconnecting the battery sometimes works as well; it’s kind of like performing a hard reboot of your computer.
Of course, you can always take the car to your mechanic to have it looked at, but that will be more expensive. It’s an easy problem to diagnose yourself, so we recommend saving your money.
Also, some cars have displays that show the pressure inside each individual tire. If the TPMS alerts you to a problem with one specific tire and that tire doesn’t actually have a problem, well, that makes it pretty easy to locate the faulty sensor.
Finding the bad sensor is only half the battle — believing in yourself is the other half. The third half, of course, is replacing the malfunctioning unit, and the fourth half is trying to remember how fractions work.
Before we do any of that, though, let’s take a look at what causes these sensors to fail in the first place.
Why Your Tire Pressure Sensor Failed
There are a variety of things that could damage a tire pressure sensor, and understanding what caused yours to fail can help you prolong the life of its replacement.
Most of the time, sensors fail due to age. They’re designed to last around 5 to 7 years before their batteries go out, so if you have your vehicle long enough, you could end up replacing the sensors a few times.
Like any other piece of equipment, excessive wear and tear can shorten their lifespan as well. The more you drive your car, the faster you’ll wear out the sensors.
They can also be damaged by corrosion on the valve stem. Certain models of Toyotas are infamous for this, as their stems can crack or break from the corrosion, causing the tire to instantly go flat.
How Much Does it Cost to Replace a TPMS Sensor?
Now that you have some idea of how you broke your sensor, it’s time to answer the most important question: how bad will it hurt to fix it?
The cost will vary depending on the make and model of your car, but in general, you can expect to pay between $200 and $300 to have a mechanic do the job for you. If you have a higher-end automobile, though, that cost can skyrocket to as much as $750 or more.
The sensors themselves are the most expensive part, as they can range from $150 to $700. The labor should cost less than $100 if you’re just replacing one, and keep in mind that you’re not obligated to replace all four sensors simultaneously.
The fact that the parts are expensive and the labor is (relatively) cheap means it usually doesn’t make sense to replace your sensors yourself, but if you decide to go that route, it’s a fairly simple process — provided you have the right tools for the job.
How to Replace a TPMS Sensor Yourself
If you plan on doing the work yourself, you’ll need all the tools you’d use to fix a flat (jack, lug wrench, crow bar, and lubricant), plus a hex-key wrench.
The instructions below assume that you’ve identified the wheel with the faulty sensor, but if you’re planning on replacing all your sensors, just repeat the steps four times.
Remove the Tire
Start by parking your vehicle on a flat surface and put blocks behind the wheels to make sure it doesn’t go anywhere at an inopportune moment.
Jack the car up and remove the affected tire, then set it somewhere where you can work on it. You’ll want to remove the tire from the rim, so lay it on the ground with the valve stem facing up.
Wedge your crowbar in between the tire and rim to break the seal, and then work around the rim, prying the rubber away from the wheel. Do this until the tire is completely dislodged, and then repeat on the other side.
This will be difficult, so you may want to lubricate the area where the tire and rim meet. Dish soap works well for this purpose. It also works well for cleaning dishes, but that’s a subject for another article (one that we hope a certain roommate will read — you hear that, Todd?!).
Remove and Replace the TPMS Sensor
You’ll see a hex nut on the exterior of the wheel, usually near the stem. Use the hex-key wrench to remove this nut and take off the faulty sensor.
Replace it with a new sensor and put the hex nut back. You’ll then need to re-seat the tire on the rim; fortunately, it’s much easier to put it back on than it is to take it off.
Lubricate the edge of the tire where it meets the rim, as this will help it pop back on more easily. Then all you have to do is air up the tire again. You’ll hear a “pop” when it gets re-seated, and once you hear that, all you have to do is air up the tire to its recommended PSI.
Reset Your Sensors
While you’re here, it’s worth checking the PSI in all your other tires as well. Once they’re all good to go, it’s time to reset the sensors.
As mentioned previously, you do this by driving. Your car’s manual will tell you exactly what you need to do, but in most cases you’ll need to drive at least 50 mph for 5-10 minutes or so. The light will go off when the system is successfully reset.
Can I Drive My Car with a Faulty TPMS Sensor?
If you know that your sensor is faulty — but your tires are fine — then there’s little danger in driving your car. At worst, you won’t be informed if your tires lose pressure, but that’s relatively unlikely to happen, so it may be a risk you’re willing to take (unless you’re changing from cold weather to warm weather).
However, if you’re not certain that your sensor is faulty, you shouldn’t push it. There might be something wrong with at least one of your tires, and driving on a bad tire can be dangerous.
Even if you’re willing to gamble with your safety, driving with a faulty tire could damage the tire, rims, or other parts of your car — and that can quickly get expensive.
Replacing the sensor shouldn’t take more than a few hours, regardless of whether you do it yourself or have a pro handle it, so there’s no reason to wait.
Do I Have to Replace My TPMS Sensors Every Time I Get New Tires?
If you drive a newer-model car, chances are the sensors will just need to be recalibrated; the tire shop usually does this for free.
In older cars, though, the calibration process can be a huge pain. It may be easier and more cost-effective to just replace the lot of them.
Also, it’s worth considering the age of your sensors when making your decision. If you’ve had them for 5-7 years already, being proactive and replacing them before they go out may save you some hassle down the line.
You may even be able to get a better deal on the replacement cost if you do it at the same time as you replace the tires, as much of the labor will already be done when the tires are swapped out.
A failing tire pressure sensor may not seem like a big deal, but it’s not something you want to ignore. Without the valuable feedback that these devices provide, you could be vulnerable to a blowout at high speeds.
Fortunately, replacing the sensors is a fairly straightforward operation, although it can be costly due to the price of the necessary parts.
Of course, you could always use the old method of determining if your tires are in trouble, but that involves waiting for one of them to go flat on an abandoned highway in the pouring rain, so we wouldn’t really recommend that option.