I. Introduction

In the automotive safety technology ecosystem, Tire Pressure Monitoring System (TPMS) sensors serve as invisible guardians, constantly protecting the core safety of vehicles. According to the Autohome article "Analysis of the Core Functions of TPMS?", tire failure ranks among the leading causes of highway accidents. By monitoring tire conditions in real time, TPMS sensors effectively reduce the risk of blowouts. Their status in modern automotive safety architecture has evolved from an optional feature to a mandatory standard. Whether for daily urban commuting or long-distance highway driving, TPMS sensors complement manual inspections with technological means, providing drivers with all-weather tire safety assurance. They also indirectly improve fuel efficiency by optimizing tire pressure, achieving the dual benefits of safety and economy. This article provides a comprehensive analysis of this core automotive safety component from five perspectives: function, types, performance, troubleshooting, and development trends.

II. The Core Functions of TPMS Sensors: The Dual Mission of Real-Time Monitoring and Safety Warning

1. Real-Time Monitoring Function

The core value of TPMS sensors lies in their precise real-time monitoring capabilities. The integrated bridge-type electronic pressure sensor acts as the "nerve ending" of the monitoring system. When tire pressure changes, the sensor's resistance varies linearly with the pressure, converting the physical pressure signal into an electrical signal that can be calculated. According to the Douyin encyclopedia entry "TPMS Sensor (Sensor for Real-Time Tire Pressure Monitoring) Encyclopedia," modern TPMS sensors now monitor both pressure and temperature. Temperature sensors often use thermistors capable of detecting temperature fluctuations between -40°C and 125°C.

The integrated monitoring of these two parameters holds significant practical implications. For example, when a tire experiences a slow leak, the pressure will gradually decrease while the temperature may rise slightly due to friction. Additionally, the "thermal expansion" phenomenon caused by tire overheating during high-speed driving manifests as a sudden increase in pressure and a persistently high temperature. As stated by Shenzhen Weifengheng Technology Co., Ltd. in its article "TPMS Sensors Can Sense Tire Pressure Changes in Real Time," through algorithmic cross-validation of dual parameters, false or missed alarms can be reduced by over 70%, particularly distinguishing between "pressure fluctuations caused by normal temperature rise" and "actual leaks."

2. Safety Warning Function

When monitoring data exceeds a preset threshold (typically ±25% of the standard tire pressure), the TPMS sensor immediately activates a warning mechanism. Its built-in wireless transmitter (mostly operating in the 433MHz or 315MHz frequency bands) encrypts and transmits the abnormal signal to the vehicle's central monitor, triggering a three-level warning:

• Level 1: A flashing dashboard icon (minor deviation).
• Level 2: A steady icon and text message (moderate deviation).
• Level 3: A flashing icon and a buzzer (serious danger).

The Douyin Encyclopedia describes this process in detail: signal transmission delay is typically ≤0.5 seconds, ensuring the driver is promptly alerted to the risk. Autohome's test data shows that vehicles equipped with TPMS have a 98% accuracy rate in warning before a tire blowout, giving the driver 3-5 seconds to react. At a speed of 120 km/h on a highway, this time allows the vehicle to travel 160-200 meters, sufficient to perform evasive maneuvers such as slowing down and changing lanes. Furthermore, the warning system can determine the fault type through data analysis. For example, if the left front wheel pressure drops suddenly, the monitor will accurately mark the fault location, preventing the driver from blindly checking.

III. Comparison of Mainstream TPMS Sensor Types: Technical Differences Between Direct and Indirect TPMS Sensors

1. Direct TPMS Sensors

Direct TPMS is the current mainstream technology, characterized by "direct measurement and precise transmission." According to technical documentation from Shenzhen Weifengheng Technology Co., Ltd., each tire valve is equipped with an independent sensor containing a built-in pressure and temperature chip and battery. This sensor directly collects internal tire data and wirelessly transmits it to an onboard receiver.
Advantages:

• High data accuracy, with a pressure measurement error of ≤±0.1 bar and a temperature error of ≤±2°C. Capable of detecting slow leaks as low as 0.5 bar/h.
• Can accurately locate a faulty tire, allowing for individual tire sensor replacement.
• Unaffected by driving conditions, monitoring is possible even when stationary.
  Limitations:
• High cost: A single set of four sensors costs approximately 300-800 yuan, 2-3 times the price of an indirect TPMS sensor.
• Battery life is limited (5-8 years), requiring specialized equipment for replacement.
• Sensor collisions during installation can easily lead to data drift.

As noted by Pacific Automotive Network in its article "What are the Types of Automotive Tire Pressure Monitoring Systems?", the direct TPMS sensor is particularly suitable for users who frequently drive at high speeds and have high safety requirements.

2. Indirect TPMS Sensor

The indirect TPMS sensor is a "low-cost solution" that leverages existing vehicle hardware. It infers tire pressure using the rotational speed difference between the ABS wheel speed sensors. When a tire is underinflated, the tread deforms, reducing its rolling radius and increasing its rotational speed compared to other tires. The system then determines the fault by comparing the speed differences among the four wheels.
Advantages:

• Low cost, requiring only a software upgrade, no additional hardware, making it suitable for economy vehicles.
• No battery loss concerns, lifetime maintenance-free.
• Easy installation, no changes to the tire structure.
  Limitations:
• Low accuracy, only able to detect critical faults where tire pressure is more than 25% below the standard.
• Response delay, requiring 3-5 kilometers of driving for stable detection, unable to monitor when stationary.
• Unable to detect simultaneous pressure loss in multiple tires (e.g., slow leaks from all four wheels), prone to false alarms.

This technology is more suitable for short-distance urban commuting, where real-time and accuracy requirements are less stringent.

3. Hybrid TPMS Sensor

The hybrid TPMS sensor is a fusion solution that leverages the strengths of the direct sensor and complements the indirect sensor. Under normal conditions, it relies on the direct sensor for real-time monitoring. When the direct sensor signal is lost or the battery is depleted, it automatically switches to indirect mode for a temporary warning. Pacific Automotive Network noted that the composite type can reduce the failure rate to below 0.5% and is currently popular in mid- to high-end models, balancing reliability and cost control.

IV. Key Performance Indicators of TPMS Sensors: A Comprehensive Analysis from Accuracy, Power Consumption, and Durability

1. Accuracy

Accuracy is the lifeblood of TPMS, and sensors based on different principles vary significantly:

• Piezoresistive: The mainstream choice, measuring pressure through changes in silicon chip resistance, with a pressure accuracy of ±0.05 bar and a temperature accuracy of ±1°C, suitable for most vehicle models.
• Capacitive: Less affected by temperature, with an accuracy fluctuation of ≤0.03 bar within the -40°C to 125°C range, primarily used in luxury vehicles.
• Piezoelectric: Fast response speed (≤10ms), but poor long-term stability, limited to special engineering vehicles.

According to the Electronic Engineering World article "Sub-1G Tire Pressure Monitoring Chip Can Effectively Prevent Tire Failure," one chip achieves a pressure accuracy of ±0.025 bar and a temperature accuracy of ±0.5°C, capable of detecting changes as small as 0.1 bar. Key factors influencing accuracy include:

• Temperature compensation algorithm (can correct for 80% of temperature interference).
• Sensor calibration frequency (factory calibration required across the full temperature range of -40°C to 85°C).
• Wireless transmission anti-interference capability (encrypted transmission reduces data loss).

2. Power Consumption

TPMS sensors rely on coin-cell batteries for power, and power consumption directly determines their service life. According to the Douyin Encyclopedia, modern sensors use power managers to intelligently control power consumption:

• Sleep mode: When the vehicle is stationary, the sensor wakes up every 15-30 minutes, consuming ≤5μA.
• Driving mode: Data is collected every 0.5-1 second, consuming ≤50μA.
• Alarm mode: High-frequency transmission in the event of an anomaly, consuming ≤200μA.

Electronic Engineering World chip data shows that a sensor using Bluetooth Low Energy (BLE) can last 7-10 years on a single CR2032 battery, while traditional RF technology can only last 5 years. Additionally, the smart wake-up function (using an accelerometer to detect vehicle start) reduces ineffective power consumption and further extends tire life.

3. Durability Indicators

The automotive tire environment can be described as "extreme": temperature fluctuations range from -40°C to 120°C, vibration acceleration reaches 20G, and resistance to mud, water, and oil is required. Sensata Technologies' "Smart Tire Solution TPMS with Bluetooth® Wireless Technology" describes its product's durability through the following design features:

• The housing is made of PA66 + glass fiber, temperature-resistant from -40°C to 125°C and UV-resistant.
• The packaging process uses laser welding, achieving an IP6K9K waterproof rating and can withstand high-pressure water jets.
• The internal components are secured with glue, capable of withstanding continuous vibrations below 2000Hz.

The Douyin Encyclopedia adds that the sensor must also undergo 100,000 inflation and deflation cycles to ensure that the valve stem connection does not loosen due to pressure fluctuations.

V. Common TPMS Sensor Failures and Troubleshooting: Solutions for Signal Loss and False Alarms

1. Common Failure Types

Autohome's article "How to Solve Tire Pressure Monitoring System Failures?" summarizes five typical failures:

• Sensor Failure: Accounts for approximately 40% of cases, often caused by internal chip damage or broken cables, commonly occurring after collisions or severe vibrations.
• Battery Depletion: Approximately 30% of cases, manifested by a gradually weakening or disappearing signal, more common in vehicles over five years old.
• Signal Interference: Approximately 15% of cases, caused by nearby strong electromagnetic equipment (such as high-voltage power lines, walkie-talkies) or co-frequency interference (multiple vehicles simultaneously alarming).
• Software Failure: Approximately 10% of cases, caused by system program errors leading to false alarms, which can be fixed by restarting or upgrading.
• Improper Installation: Approximately 5% of cases, caused by sensors not being tightened properly or misaligned, resulting in abnormal data collection.

2. Troubleshooting Methods

Troubleshooting should follow the principle of "simple first, then complex":

• Basic Inspection: Observe the instrument panel warning light pattern—a single flashing light usually indicates a signal problem, while multiple lights that are solid may indicate a system malfunction.
• Specialized Diagnosis: Use an OBD diagnostic tool to read the fault code. For example, "C1720" indicates no signal from the left front wheel sensor.
• Step-by-Step Verification:
  • Inspect the sensor for damage, looseness, and valve leaks.
  • Test the battery voltage: Normally, it should be ≥3.0V; if it is below 2.5V, it needs to be replaced.
  • Troubleshooting: Restart the system away from electromagnetic sources and observe whether normal operation is restored.

3. Troubleshooting Strategies

• Sensor Failure: Replace the sensor with the same model. Use a diagnostic tool to match the ID code (to avoid conflicts with other tires).
• Battery Depletion: Some can be replaced individually (requiring specialized tools), while most require complete sensor replacement.
• Signal Interference: Move the vehicle to an open area or upgrade the sensor to an interference-resistant model (such as one with frequency hopping technology).
• Software Issue: Visit a dealership to refresh the system software. Some models support OTA updates.
• Improper Installation: Recalibrate the sensor position to ensure alignment with the valve stem and maintain a torque of 3-5 Nm.