Tire Monitoring System: Description and Operation
TIRE PRESSURE MONITORINGDESCRIPTION
The Tire Pressure Monitoring (TPM) system monitors air pressure in the four road tires. Pressure in the spare tire is not monitored.
The system alerts the driver when tire pressure falls outside predetermined thresholds.
There is a sensor (transmitter) located in each of the vehicle's four road wheels that operates on a 315 MHz radio frequency (Fig. 17).
The TPM system is controlled by the Sentry Key Remote Entry Module (SKREEM). When Diagnosing the TPM, use a scan tool accessing the SKREEM.
An indicator lamp located in the instrument cluster and the Electronic Vehicle Information Center (EVIC) are used to communicate system information.
For further information, refer to the Owners Manual or the appropriate diagnostic information.
OPERATION
The Tire Pressure Monitoring (TPM) system uses radio and sensor technology to monitor tire air pressure levels. Sensors, mounted to each road wheel as part of the valve stem, transmit an RF signal indicating their individual pressure to a receiver located in the Sentry Key Remote Entry Module (SKREEM). These transmissions occur approximately once every minute at speeds over 15 mph (24 km/h). The Tire Pressure Monitoring system remains active even if no tire pressure related message is displayed.
The 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.
If the system detects that the tire pressure in any road tire is going low, beyond the Low Pressure (lamp) ON threshold (see following table), the TPM system will display a message in the instrument cluster and continuously illuminate an indicator lamp. This message will be displayed for the rest of the ignition cycle, or until the Low Tire pressure condition has been corrected. Once pressure in the suspect tire raises above the Low Pressure (lamp) OFF Threshold, the lamp will go out and the system returns to normal within approximately two minutes time. If the C/T, MENU, STEP or RESET button is pressed, the message is replaced by the new message requested; however, if the Low Tire condition has not been corrected, the Low Tire pressure message will again be displayed.
If a system fault is detected, the indicator lamp will flash on/off for 10 seconds, once every 10 minutes.
For further information, refer to the Owners Manual or the Appropriate Diagnostic Information.
TPM THRESHOLD PRESSURES