Toyota 2012 Yaris Hatchback Owner's Manual page 241

4-3. Do-it-yourself maintenance
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Inspection and adjustment procedure
Remove the tire valve cap.
Press the tip of the tire pressure gauge onto the tire valve.
Read the pressure using the gauge gradations.
If the tire inflation pressure is not at the recommended
level, adjust the pressure.
If you add too much air, press the center of the valve to
deflate.
After completing the tire inflation pressure measurement
and adjustment, apply soapy water to the valve and check
for leakage.
Put the tire valve cap back on.
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Tire valve
Tire pressure gauge