Tire Pressure Monitoring System (TPMS): Notes
This system monitors tire pressures and provides warning via a "Lo Tire" LCD message and an audible warning alert when a tire pressure has fallen below a predefined threshold. There are two thresholds; they are "Tire Pressure Low" and "Critical Tire Pressure." The system only operates when the vehicle is moving above 33 km/h (20 mph.) Above this speed, the Tire Pressure Monitoring system continuously monitors the air pressure in all four tires. The Tire Pressure Monitoring system will alert the driver in the event the air pressure falls below a threshold in one or more of the tires. The TPM system consists of:
- Tire Pressure Monitor Module
- Four Tire Pressure Sensor/Transmitters
- Body Control Module (BCM)
- "Lo Tire" LCD message (Instrument Cluster)
The system operates by monitoring a radio frequency (RF) transmission from the Tire Pressure Sensor/Transmitters located in each wheel, and integrated with the valve stem. A battery located inside the assembly powers the transmitter. To extend the life of the battery, the transmitter, when below 33km/h 20mph will continue to transmit for fifteen minutes then turn off, and then re-transmit once every hour. When the vehicle reaches a speed of 33 km/h (20 mph), the centrifugal force of the rotating wheel closes a roll switch (inside the transmitter) that powers up the Integrated Circuit.
Each transmitter has a unique identity (ID) code. The ID code allows the module to indicate to the driver, through the "Lo Tire" LCD message, that one of the tires has lost air pressure. The DRBIII® is used to tell which tire pressure sensor/transmitter has failed or sensed a low tire pressure based on its ID code.
Verification that the TPM system is operational must be performed during a road test, since the system only becomes operational when the vehicle exceeds 33 km/h (20 mph). The DRBIII® must not be connected during the road test. The DRBIII® can be used following the road test to check whether or not the TPM module received RF signals. The TPM module is located behind and right of the Instrument Cluster.