Remove the lower 3 screws with an Allen key wrench (they are threaded posts with an Allen key on top) , be careful they may fall into the engine never to be seen again. The center emblem can be raised slightly from the cover and unscrewed from the post below.
It
The PCV valve on a 1997 Toyota Avalon is located on top of the engine. It connects the left valve cover with the intake.
squeeze and pull down on it.
The 1998 Toyota Avalon OBD 2 port is behind fuse cover
The 1997 Toyota Avalon OBD 2 port is behind fuse cover
The 1998 Toyota Avalon OBD 2 port is behind fuse cover
The 1999 Toyota Avalon OBD 2 port is behind fuse cover
First check under the radiator for a metal cover , remove that by unscrewing few screws and then look for a drain plug , facing the engine it should be slightly on the left from the center
First try to look in the info book that came with the car, if that doesn't work see a mechanic. Or cunsult your Toyota dealer.
The camshaft position sensor is located under the hood, beneath the engine cover. The engine cover must be removed with a wrench to access the two sensor banks and their wiring harnesses.
On top of the engine, but you have to remove the cover to see them.
All fuse boxes in the Avalon have the diagram of what each fuse does on a sticker in the cover.