How does the tire pressure sensor on my car know that the tires are low?

Lottie1001

"Indirect types work by using an existing vehicle sensor, usually that of the ABS (anti-lock brake) system, to detect low pressures. Unfortunately, indirect Tyre Pressure Monitoring Systems are often not very accurate and require the driver to reset the system every time a tyre is inflated. "Direct Tyre Pressure Monitors are more common and effective. They consist of a combined tyre pressure sensor and valve unit, attached to the inside of each wheel rim. "The sensors emit a low-frequency radio signal to a receiver, the message from which is sent to the vehicle's onboard computer. The driver is then alerted if the tyre pressures fall below the prescribed limits." http://www.motoringassist.com/motoring-advice/technical-advice/your-guide-to-tyre-pressure-monitoring-systems-tpms-/ http://en.wikipedia.org/wiki/Tire-pressure_monitoring_system Dec 28 12, 11:29 AM