Hey guys, my 2016 Toyota Yaris Hybrid (German model) is fitted with a tire pressure control system which alerts you when one of your tires is losing pressure. I had issues with that system recently, so I'd like to share my experiences, maybe they are helpful to others:
The system is based on sensors in the valves of the tires. They transmit their readings by radio frequency to the onboard computer. In order to work together, the valve transmitters have to be registered with the onboard computer. The computer can deal with up to two sets of tires.
As far as it seems, the tire pressure warning light in the cockpit has three modes. As soon as you start the car, the light briefly lights up to show that it is working, then it goes off again - this is the normal behavior: No warning light, no problems.
As soon as the light goes permanently on, the tire pressure of one or more tires is out of the normal range. And as soon as the light is flashing, the system has problems reading the sensors.
You most probably come in touch with the system when you change your winter tires with your summer tires, like I did yesterday. My car was factory equipped with 195/50 tires on 16 inch rims. When I bought it in October 2019, the dealer put it on 175/65 winter tires on 15 inch rims. I stored the winter wheels with my tire dealer. Yesterday he exchanged the wheels again. And today I had a tire pressure alarm, which was both with a flashing and a permanent light. So I had both to reconnect the sensors and set the right pressure.
This is what I did:
1. Locate the secret button. There is a little black pushbutton hidden under the dashboard, it is marked "Set", and you probably won't find it without a torch.
2. Start the car. I have a Hybrid, so I start the Hybrid system. If your Yaris is not a Hybrid, just switch on the ignition.
3. While the warning light is flashing, press the set buttons three times. Do not hesitate too long, three times in one second is a good try. The warning light starts to flash slower, then it stops flashing and starts to run permanently. This is a good sign. Leave your car on at least for two or three minutes. Then switch it off.
If you switch on your car again, the tire pressure warning light should not flash anymore. Most probably it is on permanently now.
Hint: When the warning light is on permanently and not flashing, the computer can read the sensors, but something is wrong with the pressure.
4. Setting the tire pressure: You put the pressure on your tires which your users manual recommends (or which you want to have). Then you have to calibrate your tire pressure warning system to store this pressure as "normal". This is how it is done:
5. Switch on your car. The warning light starts to light up permanently. Then press the set button a few seconds, until the warning light flashes three times. Then leave the car on for two or three minutes. Then switch off the car. You are done.
You probably have to repeat this procedure when you change to wheels with a different dimension and/or with a different tire pressure. Or when your pressure sensing valves have to be replaced.