If the car was stationary for more than 15 minutes and then began to move at a speed of more than 20 km / h, each activator in turn transmits a low-frequency signal for 18 seconds in the following order:
- Front left
- Front right
- Rear right
- Rear left
Each tire pressure sensor responds in turn so that the TPMS software can locate the sensors at the beginning of the driving cycle. This procedure is repeated up to three times or less if the position of the sensors is already known. This procedure is called "automatic positioning" and takes 2 to 4 minutes.
During this time, the pressure sensors transmit a signal at regular intervals of 5 seconds (15 seconds on vehicles for North American markets). Thereafter, during the driving cycle, the pressure sensors transmit a signal every 60 seconds, or more frequently if a change in tire pressure has been detected, until the vehicle stops and the TPMS system returns to park mode.
Once the wheel position is set, the activators stop emitting a low frequency signal until the vehicle stops and the parking time exceeds 15 minutes.
A warning appears on the instrument cluster message center display if the tire pressure drops to 25% of nominal. The displayed message will also include position information (I) faulty (s) wheels (wheels).
If the vehicle speed has been below 20 km/h for 15 minutes, the TPMS will enter park mode. In park mode, the tire pressure sensors transmit a coded high frequency signal once every 13 hours. In the event of a pressure drop of more than 0.6 bar (1 lb/in2) the sensor sends a signal more often.
The spare tire pressure sensor also sends a signal every 13 hours, similar to how sensors do "workers" wheels in parking mode. In the event of a pressure drop of more than 0.6 bar (1 lb/in2) the sensor sends a signal more often.
Activators
There are 4 activators installed on the car. The front activators are located near the front of the front wheel arches, behind the fender flares. The rear activators are located at the rear of the rear wheel arches, behind the fender flares. Each activator has a connector connected to the body wiring harness.
The activator is a passive low frequency transmitter. The activators transmit their signals to the tire pressure sensors, prompting them to change the status of the mode.
TPMS excites each activator in turn using low frequency pulses. The corresponding tire pressure sensor detects a low frequency signal and changes the mode status in high frequency transmission based on this signal.
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