Description And Operation

DESCRIPTION 

The Tire Pressure Monitoring (TPM) system monitors air pressure in the four road tires (excludes spare). Sensor transmissions occur if there is a significant change in pressure. Radio Frequency Hub (RFH) module has to be awake when sensor transmits to monitor spare pressure.

The TPM system consists of tire pressure monitoring sensors attached to each road wheel through the valve stem mounting hole, an electronic display, and an indicator lamp. The system communicates through the RFH module.

The receiver circuit for the TPM system is integrated into the RFH module. If the vehicle is equipped with the remote start, the external remote start antenna receives the signal that the RFH module decodes, the radio frequency signals transmitted by each of the vehicle tire pressure sensors. The decoded information is used to determine if "warning" or "fault" conditions exist within the TPM system.

Upon detection of a warning or fault condition, the RFH module will send a request to the module that controls the indicator lamp and the text display via the vehicle bus system to illuminate or flash the indicator lamp. Also, upon detection of a warning or fault condition, the electronic display will send a request to sound the "chime".

• The RFH module will store all warning and fault conditions, placard pressure values and low-pressure threshold values (lamp ON and OFF) in memory that can be accessed through diagnostic communication. If new sensors are introduced to the vehicle, the data stored for the sensor being replaced will be deleted.
• The RFH module will store all wheel sensor IDs and locations and faults in memory that can be accessed through diagnostic communication. All other data values transmitted from each active wheel sensor shall be stored in the RFH module memory.
• The RFH module automatically learns and stores the sensor IDs while driving within 20 minutes continuously above 32 km/h (20 mph) after a sensor has been replaced. The learning sequence will initiate when the vehicle has been stopped for more than 20 minutes.

OPERATION 

The TPM system is designed to operate without loss of function for all OEM tire construction for this vehicle. 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 RFHM. Refer to SENSOR, TIRE PRESSURE MONITORING (TPM), DESCRIPTION AND OPERATION .

• If the TPM system detects that the tire pressure in any road tire is low, beyond the Low Pressure (lamp) ON threshold (see placard table below), the TPM system will continuously illuminate an indicator lamp. If a system fault is detected, the indicator lamp will flash ON/OFF for 75 seconds, then remain on solid.
• If the RFH module detects a warning or fault condition at ignition key ON, the display module will request a chime once per ignition cycle for the first "warning" or "fault" condition detected. A "warning" or "fault" condition will remain enabled until the problem causing the condition is corrected and removed/reset.
• The RFH module continuously monitors for the receipt of tire pressure RF message transmissions from the wheel sensors for 20 minutes after key OFF. The wheel sensor ID's and the location of each sensor (for example, Tire 1, Tire 2 and others) are stored in the RFH module non-volatile memory during the initial Manufacturing Plant Process (MPP), or during a service procedure, as required.
• The TPM System will continue to warn the driver of low tire pressure as long as the condition exists, and will not turn off the indicator lamp until the tire pressure is at or above the placard. The system will automatically update and the TPM indicator lamp will extinguish once the updated tire pressures have been received.
• Tire pressure will vary with temperature by about 6.9 kPa (1 psi) for every 6.5°C (12°F). This means that when the outside temperature decreases, the tire pressure will decrease. Tire pressure should always be set based on cold inflation tire pressure (placard pressure). This is defined as the tire pressure after a vehicle has not been driven for more than 3 hours (and in outside ambient temperature). The tire pressure will also increase as the vehicle is driven; this is normal and there should be no adjustment for this increased pressure. For a system fault, the system will return to normal once the RFH module receives a valid transmission from that sensor location.

TPM THRESHOLD PRESSURES 

The recommended "Placard Pressure" for the tires installed on the vehicle, are stored in the RFH module non-volatile memory during the initial MPP, or during a service procedure, as required. To determine the pressure thresholds for a vehicle, refer to the TIRE INFLATION PRESSURES  (Placard) Label, and then apply the placard pressure to the following table.

For additional information, refer to the Owner Manual or the appropriate diagnostic information.