You need to locate the the opening under your car and then either shoot some air up in the hole or use a hanger or something like it to unblock the drain.
This is one of those items that is so mysterious. Why can't the belt be inspected to see if a replacement is needed? Some folks claim they have not replaced the belt in over 150,000 miles.
Although this may be considered a general question I own a 2001 ES300 and my tire loses air to about 20lbs in about 10 days. I think its coming from around the rim. Is there a way to repair this or do I need to replace the wheel?