How does the tire pressure sensor work?

The tire pressure sensor is a crucial component in modern vehicles that helps monitor and maintain proper tire inflation. This sensor plays a vital role in ensuring safe and efficient driving by alerting drivers to any issues with their tires' air pressure.

What is a Tire Pressure Sensor?

A tire pressure sensor is a small electronic device installed inside each of a vehicle's tires. These sensors continuously monitor the air pressure within the tires and transmit this information to the vehicle's onboard computer system. The system then displays the tire pressure readings on the dashboard, allowing the driver to quickly identify any issues and take appropriate action.

How Does the Tire Pressure Sensor Work?

The tire pressure sensor uses a pressure transducer to measure the air pressure inside the tire. This transducer converts the physical pressure into an electrical signal, which is then transmitted to the vehicle's computer system. The computer processes the data and displays the tire pressure information on the dashboard, often in the form of a tire pressure monitoring system (TPMS) warning light or digital readout.

The sensor is powered by a small battery, which typically lasts for several years before needing replacement. When the battery runs low, the sensor will alert the driver, indicating that the sensor needs to be serviced or replaced.

Benefits of the Tire Pressure Sensor

The tire pressure sensor provides several important benefits for drivers:

• Improved Safety: Properly inflated tires are crucial for maintaining vehicle stability, handling, and braking performance. The tire pressure sensor helps prevent dangerous situations, such as blowouts or loss of control, by alerting the driver to any air pressure issues.


• Increased Fuel Efficiency: Underinflated tires create more rolling resistance, which can significantly reduce a vehicle's fuel economy. The tire pressure sensor helps drivers maintain optimal tire pressure, leading to improved fuel efficiency.


• Extended Tire Life: Properly inflated tires wear more evenly and last longer than those that are under- or over-inflated. The tire pressure sensor helps extend the lifespan of a vehicle's tires, saving the owner money on replacement costs.

Overall, the tire pressure sensor is a valuable safety and maintenance tool that helps drivers maintain their vehicles and ensure a safe, efficient driving experience.

How do tire pressure sensors send signals?

TPMS sensors communicate wirelessly using radio frequency (RF) signals to a receiver in the vehicle, which then sends the data to the car's computer and dashboard. The sensors, which have a unique ID, monitor pressure and temperature and transmit the data, often at specific intervals or when a significant pressure change occurs. To conserve power, they often go into a "sleep mode" when the vehicle is not moving.
 
This video explains how TPMS sensors work: 59sGM Genuine Parts & ACDelcoYouTube · May 25, 2016
How direct TPMS communication works

• Sensors and power: Each tire has a sensor with a small battery and a wireless transmitter that constantly monitors pressure and temperature. 
• Wireless transmission: When a sensor is active, it transmits a low-power radio signal (often at 315 or 433 MHz) containing its unique ID, pressure, and temperature. 
• Activation and sleep mode: Sensors are designed to conserve battery life. 
  • They typically transmit at regular intervals (e.g., every 30-120 seconds) while the vehicle is in motion. 
  • When the vehicle is parked, they often enter a sleep mode and stop transmitting until movement is detected. 
  • A sudden drop in pressure will trigger an immediate transmission, regardless of whether the car is moving. 
• Receiving the signal: A receiver in the vehicle, often using the same antenna as the keyless entry system, picks up the RF signals from the sensors. 
• Vehicle computer: The data is sent to the car's onboard computer (ECU or Body Control Module) for processing. 
• Displaying information: The computer then sends the information to the instrument cluster or dashboard, illuminating a warning light if the pressure is too low or, in some advanced systems, displaying the pressure for each tire. 

You can watch this video to learn more about TPMS sensor signals: 57sTire ReviewYouTube · Jul 13, 2023
Indirect TPMS communication

• How it works: Instead of using a separate sensor for each wheel, indirect TPMS uses the existing wheel speed sensors from the anti-lock brake system (ABS) to estimate tire pressure. 
• No wireless signal: There is no radio signal from a pressure sensor in the wheel; the system relies on detecting when one tire is rotating faster than the others, which indicates it is underinflated and has a smaller diameter. 
• No individual readings: This system can only trigger a warning light; it cannot show the individual pressure readings for each tire. 

How do tire pressure sensors know which tire is which?

TPMS knows which tire is which primarily through unique IDs assigned to each sensor, which are registered with the vehicle's computer system. Many modern systems use direct TPMS with a unique serial number for each sensor, which the car's computer associates with a specific wheel position. For other systems, such as indirect TPMS that lacks individual sensors, the car's computer identifies low pressure based on wheel speed differences measured by the ABS sensors. 
You can watch this video to learn how to identify a Tire Pressure Monitoring System: 1mDillAirControlsYouTube · Mar 7, 2013
How it works

• Unique sensor IDs: Each direct TPMS sensor has a unique serial number or ID programmed into it by the manufacturer. 
• Registration process: During the initial manufacturing or installation, the car's computer is programmed to recognize the unique ID of each sensor and associate it with a specific wheel location (e.g., front-left, front-right). 
• Location detection: In some systems, the car's computer uses a combination of the sensor's ID and the position of the receiving antenna to determine which tire is which. For example, the car may have an antenna near each wheel, and when a sensor sends a signal, the computer can identify its location based on which antenna received the signal. 
• Relearning after tire rotation: When tires are rotated, the system needs to relearn the positions of the sensors. This can often be done automatically through a few minutes of driving, or it may require a manual "relearn" procedure using a tool, according to this Reddit post and Urb's Garage. 

This video explains how TPMS sensors work in direct and indirect systems: 47sCars SimplifiedYouTube · Apr 9, 2022

Why does my tire pressure light keep coming on when my tires are fine?

Your tire pressure light may stay on even with fine tires due to a faulty sensor, a slow leak, or a system that needs to be reset. A sensor can fail from damage or age, a leak might be slow enough to be missed, or the system may simply require a recalibration after a pressure adjustment. 
Common reasons for the light to stay on

• Malfunctioning sensor: Sensors are located inside each tire and can break or wear out over time from impacts, potholes, or age. A dead battery in the sensor is also a possibility, especially in older vehicles. 
• Slow tire leak: Even a tiny leak can eventually trigger the sensor. This can be hard to detect without a pressure gauge, and the light may come on again after a while. 
• Temperature fluctuations: Significant drops in temperature can cause air inside the tires to contract, lowering the pressure and triggering the light, especially in winter. Driving for a while often warms the tires enough to turn the light off, but if it remains on, you may need to add air. 
• System needs a reset: After adding air to your tires, the system may not immediately reset. It can take a few miles of driving for the system to recalibrate. If it doesn't reset on its own, a manual reset or professional recalibration may be necessary. 
• Spare tire issues: Some cars have sensors in their spare tires as well. If the spare is being used, its sensor could be the source of the problem. 
• Incorrect pressure: While you may think your tires are fine, it's possible one or more are over-inflated, which can also trigger the TPMS light in some vehicles. 

What to do next

• Re-check the pressure: Use a reliable pressure gauge to check the pressure in all four tires (and the spare if applicable) and compare it to the recommended PSI listed on the sticker inside your driver's side doorjamb. Adjust as needed. 
• Drive for a bit: Drive the vehicle for a few minutes to allow the system to reset on its own. If the light turns off, your issue was likely a temporary fluctuation. 
• Inspect for damage: Visually inspect the tires for any signs of damage or punctures. 
• Reset the system: If the light remains on after checking, try to manually reset the TPMS through your vehicle's infotainment system or a dedicated button, as described in your owner's manual. 
• Consult a professional: If the light still won't turn off, a mechanic can scan the system to diagnose the problem, which likely involves a faulty sensor that needs to be replaced. 

How do tire pressure sensors get power?

And transmitter. And sends out a radio frequency to sensors on the vehicle. That data is sent to the vehicle's. Main computer where it can use that data to illuminate the tire.