How TPMS Works

A automotive tire pressure monitoring system (TPMS) uses sensors installed in each tire to check air pressure levels. These sensors measure the air pressure and temperature inside each tire every few seconds. The sensors then transmit the readings to a central receiver unit, usually located in the vehicle's body computer or instrument cluster. If the pressure in any tire drops by 25% or more from the recommended pressure, the TPMS alerts the driver by illuminating a low tire pressure warning light on the dashboard.

Some key parts that enable TPMS operation include:

- Sensors: Battery-powered sensors are installed in each wheel or tire during new vehicle assembly. Each sensor measures air pressure and temperature and wirelessly transmits this data.

- Receiver: A central receiver, located in the vehicle's body computer, receives wireless signals from each tire sensor. It processes the sensor data and alerts the driver if any tire is underinflated.

- Dashboard warning light: When a low pressure condition is detected, the TPMS illuminates a warning light, usually the tire pressure or TPMS symbol, on the instrument cluster. This alerts the driver to check and refill the underinflated tire.

Direct and Indirect TPMS Types

There are two main types of automotive tire pressure monitoring system - direct and indirect. Direct Automotive Tire Pressure Monitoring System uses individual sensors in each wheel to directly measure air pressure and temperature. Indirect TPMS does not have individual sensors - it estimates tire pressure based on inputs like wheel speed, steering angle and vehicle deceleration.

Direct TPMS offers more accurate pressure readings for each individual tire compared to indirect systems. However, it requires a sensor to be installed in each wheel which adds to the manufacturing cost. Indirect TPMS is more affordable as it does not need individual tire sensors but cannot detect under inflation as quickly or accurately.

TPMS Sensor Operation

Modern TPMS sensors operate using RF (radio frequency) technology for wireless communication. Each sensor is powered by an internal battery that can last 5-10 years depending on driving habits and climate conditions. When triggered by the vehicle's receiver unit, the sensor sends out a signal containing pressure and temperature readings using ultra-low frequency electromagnetic waves.

The signal passes through the wheel rim and air tire freely since radio frequencies can easily penetrate non-metallic materials. Upon receiving the RF signal, the vehicle's body computer processes the data and continuously monitors each sensor reading. If pressure falls outside the preset acceptable range of plus-or-minus 4 PSI from the vehicle manufacturer's recommended level, the driver is alerted.

Maintenance and Replacement

To function accurately long-term, TPMS requires periodic sensor battery replacement. Typically, sensor batteries last the lifetime of one or two sets of tires depending on driving habits and environmental factors like temperature extremes. Garages can check battery levels using TPMS diagnostic tools. Low battery is the most common cause of TPMS malfunctions.

Damaged or worn out TPMS sensors also need replacement. This happens when a wheel/tire undergoes repair like replacing a punctured inner tube or refitting after a flat tire. The removed sensor must be transferred to the new wheel assembly. Not replacing the tire sensor can disable the TPMS in that wheel. Replacement sensors must be reprogrammed to sync with the vehicle's receiver.

Safety Benefits of Automotive Tire Pressure Monitoring System

The key benefit of TPMS is enhanced vehicle safety from under-inflated tires. Driving with low pressure dramatically reduces tire tread life. It also increases braking distances, reduces traction and steering control. All this raises risks of accidents. TPMS alerts the driver to potential tire problems early on, allowing timely remedial action before a safety incident occurs.

Properly inflated tires roll with lower resistance for better fuel efficiency too. TPMS thus helps improve economy besides alerting drivers to dangerous low pressure conditions. As a result, transportation authorities now mandate TPMS fitment on all new passenger vehicles for enhanced road safety. Modern cars cannot be sold without a functional tire pressure monitoring system.

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