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The Truth About Tire Pressure or TPMS Sensors

The Truth About Tire Pressure Or TPMS Sensors

As the weather changes around Springfield, you may notice your tire pressure showing up on your dashboard. As the temperature warms and cools, it can cause small leaks and your make your tires loose pressure.

Starting in 2008, federal regulations required all news cars to be equipped with TPMS sensors, or a Tire Pressure Monitoring System. The goal was to alert drivers to dangerous changes in tire pressure, reducing emergency roadside problems.

If you have one of these systems, you likely know it is a matter of when, not if, it will require your attention. Before you jump in thinking you will take this on as a DIY repair, be sure you know a little more about the system.


What Do Tire Pressure Or TPMS Systems Actually Measure?

Not all TPMS sensors actually measure tire pressure. Rather, there are to different types of systems, direct and indirect monitoring.

The direct monitoring system measures the actual tire pressure. It has a sensor on each wheel that also measures temperature and sensor battery life.

The indirect system has a sensor at each wheel, but they are part of the ABS system. These sensors actually measure the rotational speed of the tire. The onboard computer then uses an algorithm to calculate the tire pressure based on the rotational speed.

The goal of the system is to alert the driver when the tire pressure is 25% less than the manufacturer recommended pressure. In most cars, this will activate a warning light on the dashboard.

If the recommended pressure for your tires is 35 psi, then it should activate around 26 psi. At this reduction in pressure, you risk damaging the tire if you hit a hole, not to mention causing excessive wear on the inside and outside shoulder of the tire.


How The Information Is Relayed

As the sensor captures the information, it is relayed back to the onboard computer using a radio frequency. The two frequencies commonly used are 315 MHz and 433 MHz. The correct frequency for your system will be stamped on the sensor itself, and may be listed in your owners manual.

These frequencies are not interchangeable, so it is important to get the correct one for your vehicle. Installing the wrong sensor will waste money being you cannot return parts already installed, and leave the warning light on your dashboard.


Installing New TPMS Sensors

Replacing your sensors is more involved than just matching the correct frequency. Rather, some manufacturers design the receiving system to only work with certain OE manufacturers.

Some aftermarket manufacturers make multi-platform sensors, allowing them to work with several systems. Before purchasing one of these, be sure you know it will work with your particular vehicle. Also, consider whether a special tool is required to program the sensor to work with your vehicle.


Activating Your New Sensor

Being the sensors are battery operated, they are usually shipped in storage mode to preserve the battery life. This means they must be activated before they will begin, which is not simply pulling a plastic tab out before installing the sensor.

Some systems require the use of a TPMS activation tool that uses a 125MHz frequency. There is a special manufacturer’s tool with a modulated 125MHz frequency if your vehicles uses the TRW sensors.

In some cases, the sensors are activated by pressure. Once you have the pressure installed, you simply inflate the tire above 25 psi to bring them out of storage mode. While these are convenient, you must make sure they are the right kind for your vehicle.


Pairing Your Sensors to Your Car

Pairing your sensors to your car can be even more challenging than activating them. This process not only pairs the sensor to your system, but also allows your system to match the sensor to the location.

The easiest of these systems is the auto location system. With this particular system, you simply have to drive the vehicle above 12 mph for at least 15 minutes, and the system will learn each new sensor.

Your system may use a manual entry system. These require a compatible scan tool to manually enter the sensor identifier and location.

Some systems require a special activation tool. This requires the system to be put into a training mode, and then assign each sensor to its location.

The other option is a special activation magnet that fits over the valve stem once the tire is remounted. The computer must still be put into a training mode, but then the magnet allows the sensor ID to be recorded by the system.

Each of these systems have their peculiarities, but are not cross-compatible. Be sure you know which system your vehicle uses before purchasing replacement sensors.


TPMS Service With a Mobile Tire Repair Service

Replacing these sensors can be a pain if you are not sued to replacing tires. MTS Express offers mobile tire repair services, including tire pressure monitoring sensors. Our certified technicians come right to your home or office around Springfield, and handle the repair without you having to interrupt your day. Call to schedule a visit from one of our technicians today.

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