Lexus GS430 User Manual page 151

EXTERIOR EQUIPMENT
G15016
2. To remove the fuel tank cap, turn the cap slowly
counterclockwise by 90 degrees (to the pressure point
1 , then turn it additional 30 degrees (to point 2 ).
Pause slightly before removing it.
It is not unusual to hear a slight swoosh when the cap is
opened.
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3. The removed cap can be stored on the back side of the
fuel filler door.
Position the cap so that the hooks point to the left and right, and
set it in the receptacle on the back side of the door.
When installing the cap, turn the cap clockwise until you
hear a click. When you hear the click, the cap is fully
closed.
If the cap is not installed securely, the malfunction indicator
lamp comes on. Make sure the cap is tightened securely.
The indicator lamp goes off after driving several times. If the
indicator lamp does not go off, contact your Lexus dealer as
soon as possible.