Tire Monitoring System: Description and Operation
TIRE PRESSURE MONITORING - SERVICE INFORMATIONDESCRIPTION
The Tire Pressure Monitoring (TPM) system monitors air pressure in the four road tires (excludes spare). Pressure in the spare tire is not monitored. There are two systems available on this vehicle, a base and a premium. The base system does not specify how many tires are low or where they are located. The premium system does so.
TPM alerts the driver when tire pressure falls below predetermined thresholds.
The TPM systems are controlled by the Wireless Control Module (WCM), commonly referred to as the Sentry Key Remote Entry Module (SKREEM).
There is a sensor (transmitter) in each of the vehicles four road wheels that operates on a 315 MHz radio frequency Export vehicle sensors operate on a 434 MHz radio frequency.
If a vehicle is equipped with the premium TPM system, transponders located in three of the four wheel wells of the vehicle are used to provide the WCM with the location of the tire pressure sensors on the vehicle. The transponders are located in the left front, right front and right rear wheel wells.
An indicator lamp located in the instrument cluster and, if equipped with the premium TPM system, 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 Wireless Control Module (WCM), commonly referred to as 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. Sensors will also transmit when a pressure change of one psi (seven kPa) or more is detected during that period.
If the vehicle is equipped with the premium TPM system, transponders located in three of the four wheel wells of the vehicle are used to provide the WCM with the location of the tire pressure sensors on the vehicle. The transponders are located in the left front, right front and right rear wheel wells. A fourth transponder is not necessary in the remaining wheel well due to the process-of-elimination theory. Once the system knows the location of the first three sensors it assumes the location of the fourth tire pressure sensor is in the left rear tire.
If the system detects that the tire pressure in any road tire is going low, beyond the Low Pressure (lamp) ON threshold (see following tables), the TPM system will continuously illuminate an indicator lamp. If equipped with the premium TPM system, a message will be displayed in the instrument cluster. The text message will indicate which tire is low and the display will show all current tire pressures, the low tire will be flashing with its pressure value. This message will be displayed for the rest of the ignition cycle, or until the Low Tire pressure condition has been corrected. A chime will sound upon initial detection. 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 a message center 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 60 seconds, once every 10 minutes.
For further information, refer to the Owners Manual or the Appropriate Diagnostic Information.
NOTE: Each of the following TPM Threshold Pressure Tables corresponds to a specific placard tire pressure. To use the correct table, refer to the Tire And Loading Information label attached to the driver's door opening (B-pillar) of the vehicle being serviced.
TPM THRESHOLD PRESSURES - PLACARD PRESSURE 30 PSI (207 KPA):
TPM THRESHOLD PRESSURES - PLACARD PRESSURE 32 PSI (221 KPA):
TPM THRESHOLD PRESSURES - PLACARD PRESSURE 36 PSI (248 KPA):
