How Tire Pressure Monitoring Sensors Communicate with the Car

Tire Pressure Monitoring System (TPMS) sensors typically communicate with the car using low-power radio signals—most commonly at 315 MHz or 433 MHz for “direct” systems, and increasingly via Bluetooth Low Energy (BLE) in some newer models—sending pressure and temperature data along with a unique sensor ID to a receiver that feeds the vehicle’s control network. In “indirect” systems, no radio sensors are used; instead, the car infers pressure changes from wheel-speed data. Here’s how both approaches work, why different frequencies and methods are used, and what happens to the data once the car receives it.

Two Ways Cars Monitor Tire Pressure

Automakers use one of two architectures: direct TPMS, which relies on radio-enabled sensors inside each wheel, and indirect TPMS, which deduces pressure changes from ABS/ESC wheel-speed sensors. Understanding the distinction helps explain the communication path.

• Direct TPMS: A battery-powered sensor in each wheel measures pressure (and usually temperature and motion) and transmits radio packets to a receiver in the vehicle.
• Indirect TPMS: The vehicle uses existing wheel-speed data to detect changes in rolling radius that correlate with underinflation; no tire-mounted radios are involved.

Because direct TPMS can report actual pressure per wheel, it’s now the dominant approach globally, while indirect TPMS remains a lower-cost option that provides warning-only functionality without precise readings.

How Direct TPMS Radio Works

Frequencies, modulation, and data packets

Most direct TPMS sensors transmit in the unlicensed ISM bands: 315 MHz (historically favored in North America) or 433 MHz (common in Europe and many other markets). Modern vehicles may use either frequency regardless of region. The signals are typically modulated using ASK or FSK, and the data are encoded (often with Manchester encoding) with a checksum/CRC to ensure integrity. Each sensor has a unique ID so the car can tell wheels apart and ignore other vehicles.

When a sensor sends a packet, it includes several key fields that the car needs to evaluate tire health and manage alerts.

• Unique sensor ID (so the car can associate data with a specific wheel)
• Tire pressure (usually in kPa or psi)
• Tire temperature (used for diagnostics and sometimes pressure compensation)
• Battery status (to flag low sensor battery conditions)
• Acceleration or motion flag (to control when and how often to transmit)
• Status/diagnostic bits (e.g., sensor faults, learn mode)
• CRC/checksum (to verify data integrity)

This standardized structure allows the receiver to validate the packet, link it to a wheel position, and forward reliable data to the vehicle network for display and alerts.

Transmission timing and triggers

To preserve battery life while staying responsive, TPMS sensors transmit periodically and also on certain events. They use motion detection and pressure-change thresholds to decide when to speak up.

• Periodic beacons: Commonly every 30–60 seconds while the vehicle is moving; much slower at rest (e.g., several minutes apart).
• Event-driven bursts: Faster reporting when pressure drops quickly (e.g., a puncture) or after a significant temperature change.
• Low-frequency (LF) wake-up: A 125 kHz signal from the car or a service tool can wake a sensor, prompt immediate transmission, or help with wheel-position learning.

This hybrid schedule conserves the coin-cell battery (often designed for 7–10 years) while ensuring rapid warnings when a tire loses air.

Position learning and wheel localization

Because radio packets travel through the air, the car needs a way to know which wheel sent which packet. Many systems use 125 kHz LF antennas near each wheel well to trigger nearby sensors, letting the car correlate responses to a specific corner. Others infer position from signal strength patterns and acceleration cues (e.g., comparing rotational signatures front vs rear) after a short drive.

Power management and lifetime

TPMS sensors rely on sealed lithium coin cells. To stretch life, sensors sleep when stationary, transmit infrequently, and use motion accelerometers to wake up when the vehicle rolls. Harsh heat/cold, heavy-duty usage, and frequent event transmissions can shorten service life; ultimately, the sensor battery is not user-replaceable and the sensor is replaced as a unit.

BLE-based TPMS in Newer Vehicles

Some recent models, including several EVs (for example, Tesla Model 3/Y and refreshed S/X) and select other manufacturers, use Bluetooth Low Energy instead of 315/433 MHz RF. These sensors broadcast in the 2.4 GHz band using BLE advertising frames at set intervals, sometimes with vendor-specific data formats. Depending on the design, the vehicle may pair/bond for encrypted links or simply filter proprietary advertisements with whitelisted IDs. BLE can simplify sourcing and enable richer diagnostics, but it must contend with crowded 2.4 GHz spectrum; automotive gateways mitigate this with filtering and antenna placement optimized for the cabin and wheel wells.

What the Car Does with the Signal

On the vehicle side, a dedicated RF receiver or integrated body/telemetry gateway collects sensor packets and forwards them to the TPMS control logic, which then communicates over the in-vehicle network (often CAN) to the instrument cluster or infotainment display. The software validates CRCs, de-duplicates packets, applies temperature/vehicle-speed filters, and compares pressures against thresholds derived from the tire-load placard and regulatory standards. Some vehicles show per-wheel pressures; others only illuminate a warning lamp when any tire is under-inflated beyond a set margin.

Indirect TPMS: When There Are No Radio Sensors

Indirect TPMS avoids tire-mounted transmitters altogether. Instead, it analyzes ABS/ESC wheel-speed signals to detect changes in effective rolling radius—under-inflated tires rotate slightly faster at a given speed. Algorithms compare wheels and track patterns over time to flag a low tire.

While this approach is cost-effective and needs no sensor batteries, it cannot report actual pressure values and usually requires a driver-initiated calibration after adjusting pressures or rotating tires. It’s primarily a warning system rather than a measurement system.

Interference, Range, and Reliability

Direct TPMS is designed for short-range, in-vehicle reception. Typical range is just a few meters, and antennas are positioned to favor signals from inside the wheel wells. Occasional interference from other 433/315 MHz devices (or 2.4 GHz sources for BLE) is mitigated with repeated transmissions and filtering. Common failure modes include depleted sensor batteries, damaged valve stems, corrosion, or broken accelerometers; these typically trigger a TPMS fault or loss-of-signal message rather than a simple low-pressure warning.

Security and Privacy Considerations

Classic 315/433 MHz TPMS often transmits unencrypted, authenticated only by the sensor’s unique ID and basic checksums. This makes passive eavesdropping and even spoofing theoretically possible, and the fixed IDs can enable tracking in research settings. Some newer implementations, particularly BLE-based systems, can use link-layer encryption and whitelisting, though practices vary by manufacturer. In all cases, the risk to core vehicle systems is mitigated by gateway isolation and strict message validation, but privacy and spoofing remain areas of active improvement.

Service, Relearn, and Aftermarket Sensors

After tire rotation, sensor replacement, or seasonal wheel swaps, the car may need to (re)learn sensor IDs and positions. Automakers support several relearn strategies, and aftermarket tools can simplify the process for multi-brand shops.

• Auto-learn while driving: The vehicle observes IDs and infers positions over a short drive.
• LF-triggered learn: A 125 kHz tool activates each wheel’s sensor in sequence to bind IDs to corners.
• OBD-assisted learn: A scan tool writes sensor IDs to the TPMS module via the diagnostic port.
• Cloneable sensors: Aftermarket sensors can copy an original ID, avoiding ECU relearn in some cars.

Following the correct relearn method ensures the car associates each sensor with the right wheel, preserving accurate per-corner alerts and displays.

Summary

Most TPMS sensors communicate with the car via short-range radio: either legacy 315/433 MHz transmissions or, in some newer models, Bluetooth Low Energy. Each direct sensor sends pressure, temperature, and status with a unique ID at timed intervals and during pressure events; a 125 kHz LF signal can wake or localize sensors for service and wheel-position learning. The vehicle’s receiver validates and routes this data to the TPMS logic, which triggers warnings or shows per-wheel values. Indirect systems skip radios entirely and infer pressure loss from wheel-speed behavior, offering alerts but not exact pressures. Together, these designs meet safety regulations while balancing accuracy, battery life, cost, and robustness.

How are TPMS sensors programmed?

TPMS sensors are programmed using a TPMS scan tool to copy the unique ID of old sensors to new ones (cloning), program new IDs for aftermarket sensors, or configure a universal sensor for a specific vehicle before installation. After programming, a “relearn” procedure is necessary, which uses the same scan tool to make the vehicle’s computer recognize the new sensor’s data and location, often requiring a short drive or a specific tool function to complete the process. 
1. Understand Sensor Types 

• OEM (Original Equipment Manufacturer) sensors: Opens in new tabCome pre-programmed for a specific vehicle and do not need a separate programming step. 
• Programmable/Universal sensors: Opens in new tabBlank initially and require programming for the vehicle’s make, model, and year. 
• Pre-programmed/Ready sensors: Opens in new tabCome pre-loaded with a range of protocols and can often skip the programming step. 

2. Programming the Sensor

• Cloning: Opens in new tabThis method copies the unique ID from an old, functional sensor and writes it to the new sensor. This is useful if the old sensors are dead, as their IDs are stored in the car’s computer and can be retrieved. 
• Direct Programming: Opens in new tabA TPMS tool is used to input new, unique sensor IDs directly into the new sensor, which are then programmed into the vehicle’s computer. 

This video demonstrates how to program TPMS sensors by cloning, which copies the ID from an old sensor to a new one: 59sDIY DanYouTube · Sep 5, 2022
3. The Role of the TPMS Tool

• A specialized TPMS scan tool is essential to perform the programming. 
• The tool connects to the vehicle’s OBD-II port to retrieve or write sensor information to the car’s computer. 
• It is used to “wake up” or trigger the sensors to gather data. 

4. The “Relearn” Procedure 

• Crucial Step: After programming and installing the sensor, the vehicle’s computer needs to register it. 
• How It Works: The TPMS tool guides you through a relearn procedure to update the vehicle’s system with the new sensor’s ID and location. 
• Methods: Some vehicles offer automatic relearning after a short drive, while others require using a TPMS tool to trigger and register each sensor individually. 

How do TPMS sensors communicate with the module?

Tire pressure sensors send signals using tiny radio transmitters embedded within the tire. These TPMS sensors constantly monitor the air pressure inside the tire, and if it drops too far, they send a radio signal with the pressure data to your vehicle’s onboard computer.

How does TPMS talk to a car?

TPMS stands for tyre pressure monitoring system, it consists of small electric sensors fitted to each wheel of the vehicle to monitor tyre pressure and feed this data back to the car. Should one or more tyre see a change in air pressure, the system will show a yellow warning light on the dashboard to alert the driver.

How often do TPMS sensors send a signal?

TPMS sensors generally transmit data every 30-120 seconds when the vehicle is in motion and may transmit less frequently when parked, with some systems sending a signal immediately upon detecting a sudden pressure change. The exact transmission rate varies by vehicle manufacturer and system type, but a sudden pressure loss will always trigger an immediate transmission regardless of the sensor’s normal mode. 
Factors influencing transmission frequency: 

• Vehicle motion: When a wheel starts to roll, accelerometers in the sensor activate it to broadcast at regular intervals (rolling mode).
• Parked mode: While stationary, sensors may transmit less frequently or only in response to a significant pressure change, a behavior designed to conserve battery life.
• Sudden pressure loss: If a sensor detects a rapid drop in tire pressure, it will immediately send a signal, even if the vehicle is stationary.
• Manufacturer settings: Each manufacturer programs the sensor’s behavior, including its transmission interval, to meet the needs of their vehicle systems.

How the signal works:

• Low-frequency activation: Opens in new tabA low-frequency (LF) signal from a TPMS tool is often used to “wake up” or activate the sensor when needed for service or diagnosis. 
• UHF broadcast: Opens in new tabOnce activated or in rolling mode, the sensor transmits data via a UHF radio signal to the vehicle’s onboard computer. 
• Data included: Opens in new tabThe transmitted signal contains the sensor’s unique ID, the tire pressure, and sometimes the tire temperature.