Tire Monitoring System: Description and Operation: Description and Operation

Tire Pressure Monitoring System (TPMS)

NOTE: For 2007 model year, the tire pressure monitoring system (TPMS) is not available on vehicles having recommended tire pressures that are different for the front and rear tires (for example, front tires: 345 kPa [50 psi] and rear tires: 414 kPa [60 psi]).

The TPMS includes:
^ the vehicle security module (VSM), TPMS functionality is integrated within the VSM.
^ four tire pressure sensors.
^ four tire pressure sensor cradles.
^ four tire pressure sensor straps.
^ an instrument cluster indicator.
^ a message center (if equipped).

TPMS System Module
The VSM contains the TPMS functionality. Refer to Tire Pressure Monitoring System in Diagnosis and Testing for TPMS fault diagnosis and repair.

The VSM compares the information of each tire pressure sensor transmission against a pressure limit. If the VSM determines that the tire pressure has fallen below the low limit, the VSM communicates this to the instrument cluster on the vehicle communication bus.

TPMS Pressure Sensor
The VSM monitors the air pressure in the 4 road tires with tire pressure sensors. The sensors transmit radio frequency (RF) signals to the VSM approximately every 60 seconds when the vehicle speed exceeds 32 km/h (20 mph).

The tire pressure sensors are battery operated and are mounted to metal brackets (called cradles) on the wheels inside the tires. The sensors are mounted 180 degrees from the valve stem.

The tire pressure sensor can be serviced separately from the cradle and the strap.

TPMS Pressure Sensor Cradle
The tire pressure sensor cradles are mounted to the wheels with metal straps and have an adhesive strip to aid in their retention to the wheel.

To service the sensor cradle, the strap must also be removed.

TPMS Pressure Sensor Strap
The sensor strap is what keeps the sensor and the cradle retained to the wheel. A factory-installed strap is joined together with a one-time use buckle and a dealer-installed strap is joined together with a worm gear (similar to a radiator hose clamp). Both straps should be discarded after removal and should not be re-used.

The strap can be serviced separately from the sensor and the cradle. The sensor is available separately from the cradle and the strap. The cradle and strap are available as a strap kit. There are several different strap kits available based on wheel diameter, all strap kits share the same base part number.

Instrument Cluster and Message Center
The instrument cluster illuminates the TPMS indicator when it receives a message from the VSM to do so and displays the appropriate message(s) in the message center (if equipped).