Tire Pressure Sensor: Description and Operation
SENSOR - TPMDESCRIPTION
On vehicles equipped with Tire Pressure Monitoring (TPM), one tire pressure sensor is mounted to each wheel in place of the traditional tire valve stem (Fig. 18). Each sensor has an internal battery that lasts up to 10 years. The battery is not serviceable. At the time of battery failure, the sensor must be replaced.
The TPM system operates on a 315 MHz radio frequency (Fig. 18).
The TPM sensors are designed for original style factory wheels. Do not attempt to install a tire pressure sensor in an aftermarket wheel.
The serviceable components of the tire pressure sensor are (Fig. 19):
- Sensor-To-Wheel Seal and Metal Washer
- Valve Stem Cap
- Valve Stem Core
- Valve Stem Nut
The valve stem caps and cores used are specifically designed for the tire pressure monitoring sensors. Although similar to standard valve stem caps and cores, they are different. The valve stem cap has a special seal inside to keep moisture and corrosion out. The valve stem core has a special nickel coating to protect from corrosion.
OPERATION
The battery operated tire pressure sensors lay dormant (Park Mode), then wake and start transmitting (Drive Mode) when the vehicle first reaches speeds over 15 mph (24 km/h). Once the wheels stop rotating for a period of approximately 20 minutes, the sensors shut down until again awaken. Although not transmitting as when in Drive Mode, while in Park Mode, the sensors still transmit approximately once every 13 hours to let the receiver know air pressure status at that time.
Using an RF signal, each sensor transmits tire pressure data approximately once every minute. Each sensor's (transmitter) broadcast is uniquely coded so that the Sentry Key Remote Entry Module (SKREEM) can monitor the state of each of the sensors on the four rotating road wheels. The SKREEM automatically learns and stores the sensor's ID while driving after a sensor has been replaced. There is no formal retraining procedure necessary.
For additional information, refer to appropriate diagnostic information.