I'm missing (another) piece. I've discovered a lot of missing underbody pieces since buying this used Prius. Here's photo from ebay of what I think it is, and photos of under the car, where I think it goes. Any advice re installation/identification would be appreciated! Look for the green tab/hole. I think that's one of the places where it would attach. It's a passenger side photo, bumper on right of photo.
07 2007 Toyota Prius Lower Engine Cover - Body Sheet Metal - Action Crash, Left - Driver Side, Lower Center, Right - Passenger Side - PartsGeek It is installed with nylon plastic "push" rivets and M6 screws with 10mm heads.
You need a left and right splash shields. They are attached with bolts and clips. The shields attach to the bumper cover with bolts through a 'S' clips. I think the bolts used to attach are M6. The bolt that attaches to the green tab is a self tapping bolt not a machine bolt like the ones use in the S-clips. I think there are two or three (I doing this from memory and do not have the car as reference) additional plastic clips that attach the back of the shield to the metal frame.
