The follow codes are entered at the Main menu, if you enter it properly, the screen shoould flicker....
All leagues, tracks, and snowmobiles
hold R and press Up, Triangle, Up, Triangle, Up, Triangle
ATV
Hold R1 and press Up, Right, Down, Up, Right, Down
Cartoon track
hold R and press Right, Up, Left, Circle, Triangle, Square
Demo mode
hold R1 and press Up(3), Down(3)
Go-Cart
Hold R1 and press Right(2), Left(2), Right(2)
Summer track
old R and press Triangle, X, Circle(2), X, Triangle