Pontiac 2004 Bonneville - Manual (Page 285)

The tethered fuel cap is located behind a hinged fuel
door on the driver’s side of the vehicle. While refueling, hang the tethered fuel cap on the hook
on the inside of the fuel door.
To remove the fuel cap, turn it slowly to the left
(counterclockwise). The fuel cap has a spring in it; if
you let go of the cap too soon, it will spring back to
the right.
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