What is a TPMS Sensor? How do you Replace Them?

Under-inflated tires can pose a huge risk to your driving safety. That’s because when tires are under-inflated, friction increases at the point where the tire grips the pavement, thereby potentially resulting in everything from premature tread wear to sudden blowouts. The dangers associated with under-inflated tires are a large part of the reason why the U.S. government OK’d the Transportation Recall Enhancement, Accountability and Documentation Act. Better known as “TREAD,” the act called for vehicles sold in the U.S. to incorporate some sort of tire pressure monitoring sensor, or TPMS, into models.

Hence, after starting your vehicle – particularly on a winter morning, being that cool air can cause tire pressure to drop – you might hear a ding and see a yellow symbol light up on your dashboard. The symbol is horseshoe-shaped with an exclamation point in the middle. This is the TPMS signaling that one or more of your tires has low pressure.

Now, just because the TPMS light isn’t on doesn’t mean that your tires are either over- or under-inflated, but the TPMS can help you identify and resolve problems with under-inflation. And when the light does come on, you should take action.

Direct vs. Indirect TPMS

There are two types of TPMS: direct and indirect.

Indirect TPMS uses wheel speed sensors to assess whether or not the tires are inflated properly. It uses the same sensors that the anti-lock brakes system does, as these sensors measure wheel revolutions to determine tire size and performance. If one wheel is spinning faster than another, the system will alert the driver that the tire is under-inflated. Essentially, an indirect TPMS doesn’t monitor pressure so much as it monitors tire revolutions. Indirect sensors are more affordable but are less accurate and reliable than direct sensors.

Direct TPMS actually uses pressure monitoring sensors to assess tire pressure. The sensors then send the data to a control unit which assess the readings and determine if any tires are under-inflated. Direct TPMS tend to be more reliable and accurate, which is an advantage over indirect TPMS. However, they’re also more expensive, come with a battery that’s hard to change (though it lasts about a decade), and are apt to be more easily damaged during tire changes and rotations.

Replacing the TPMS: A How-To Guide

In addition to a replacement sensor, you’ll need a ratchet/socket set, valve core remover, torque wrench, and tire jack.

  1. Take your valve core remover and remove the valve core from the TPMS. This will cause the tire to deflate.
  2. Grab your ratchet/socket set and remove the TPMS.
  3. Pull the valve of the TPMS sensor into the rim of the tire. The sensor should drop into the tire’s base.
  4. Break the bead of the tire using the jack and then raise the top half off. Reach into the tire and remove the old sensor, and discard it accordingly. You can then properly reattach the tire to the rim.
  5. Your new sensor should come with a rebuilding kit. Start by taking the gasket from this kit and placing it into the valve of the new TPMS.
  6. Next, push the TPMS into the valve hole, then screw the hardware you removed when taking out the old sensor back into place. Use the ratchet for reassembly.
  7. Take your torque wrench and, following manufacturer recommendations, fix the wrench to the appropriate pressure and tighten.
  8. Last, you’ll need to re-inflate the tire to its proper pressure and conclude by configuring the new TPMS.

Changing the TPMS is fairly manageable if you know your way around a car, and if you’re looking for warehouse-quality direct and indirect TPMS, head over to Power Parts 4 Less to browse the company’s wide range of affordable replacement sensors.