Hit and run teen fiction book?

Ok in the book there were a group of friends and they went out driving and got into a car accident. One of the boys in the book suffers severe memory loss, and he has no recollection of his girlfriends death in the accident. I think it involved a hit and run may have just been a crash. I do remember that they were three people in the car. I liked the book when I first read it, but I cannot remember the title or author. Sorry for the vague description it's been a long time since I read the book.