What Is A TPMS Sensor?

Dustin Hawley | Jul 17, 2023

A TPMS (Tire Pressure Monitoring System) sensor is a device that is installed in a vehicle's tires to monitor the air pressure and temperature of the tires. The primary function of the TPMS sensor is to alert the driver when the tire pressure is too low or too high, which can help improve fuel efficiency, extend tire life, and enhance vehicle safety. Running with low tire pressure can cause uneven wear on the tires, increase the risk of blowouts and accidents, and decrease fuel efficiency.

What Is A TPMS Sensor

How Does a TPMS Sensor Work?

TPMS sensors, typically installed inside the tire's air valve stem, can be either mechanical or electronic. The mechanical TPMS sensors use a diaphragm and a spring to sense the pressure changes. In contrast, the electronic sensors use a battery-powered device that transmits a signal to the vehicle's onboard computer.

The sensor measures the tire's air pressure and temperature and sends this information wirelessly to the vehicle's onboard computer. The computer compares the information to the recommended tire pressure for the vehicle. If the pressure in one or more tires is too low, the computer will signal the driver via a warning light on the dashboard.

When the driver stops to inflate the tire, the sensor will automatically recalibrate, and the warning light will turn off.

TPMS sensors need to be calibrated and maintained, and the batteries on the sensors need to be replaced periodically to ensure that the system is working correctly. TPMS sensors can become damaged or lose their accuracy over time and must be replaced. Also, if the tires or wheels are replaced or rotated, the sensors must be re-calibrated or replaced to work correctly.

Types Of TPMS Sensors

There are two main types of TPMS sensors: direct and indirect. Direct TPMS sensors are installed inside the tire and directly measure tire pressure. They use a battery-powered transmitter to send a signal to the vehicle's onboard computer, which displays the tire pressure information on the dashboard or instrument panel. Direct TPMS sensors can be either mechanical or electronic. Mechanical sensors use a mechanical link between the sensor and the valve stem, while electronic sensors use wireless technology.

Indirect TPMS sensors monitor the wheel speed and infer the tire pressure based on changes in the wheel's rotation. They are installed on the vehicle's wheel hub or brake rotor, using its ABS (Anti-lock Brake System) sensors to measure the wheel speed. Indirect TPMS sensors are less accurate than direct TPMS sensors and may not detect slow leaks.

Some vehicles come with a combination of both types of sensors depending on the manufacturer's design. Some newer vehicles are equipped with TPMS sensors integrated into the tire pressure monitoring valves, eliminating the need for a separate sensor.

Symptoms Of A Faulty TPMS Sensor

The symptoms of a faulty TPMS sensor can include the following:

  • Warning light on the dashboard: If the TPMS sensor is not working correctly, the warning light on the dashboard will typically illuminate, indicating a problem with the system.
  • Incorrect tire pressure reading: If the sensor is not functioning correctly, it may give an incorrect reading of the tire pressure, leading to incorrect information being displayed on the dashboard.
  • Inaccurate or no tire pressure readings: If the sensor is malfunctioning, it may not be able to transmit a signal to the vehicle's onboard computer, leading to no readings or inaccurate readings on the dashboard.
  • Warning light stays on even after inflating the tires: If the sensor is faulty, the warning light may not turn off even after the tires have been inflated to the correct pressure.
  • The warning light turns on and off intermittently: If the sensor is not working correctly, it may give inconsistent readings, causing the warning light to turn intermittently.

It's important to note that other issues can also cause these symptoms in the tire pressure monitoring system, such as a malfunctioning receiver or a problem with the vehicle's onboard computer. It's always best to have the TPMS system inspected by a professional if you suspect a problem.

Summary

TPMS (Tire Pressure Monitoring System) sensors are devices installed in a vehicle's tires to monitor the air pressure and temperature of the tires. They send a signal to the vehicle's onboard computer, which then displays tire pressure information on the dashboard or instrument panel. Direct sensors are installed inside the tire and measure the tire pressure directly, while indirect sensors monitor the wheel speed and infer the tire pressure based on changes in the wheel's rotation. 

A faulty TPMS sensor can cause the tires to be under-inflated or over-inflated, which can increase the risk of a blowout or accident, decrease fuel efficiency, cause uneven tire wear, reduce handling and stability, give incorrect readings and be costly. To maintain and troubleshoot TPMS sensors, regularly check tire pressure, calibrate and reprogram sensors after tire replacement, clean and inspect valve stems, replace batteries in sensors, check for signal interference and have a professional inspect and diagnose any issues.

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