All Cars
At the title screen, hold L1 + L2 + R1 + R2. If entered correctly, you will hear a sound. Immediately hold Up + Triangle, while keeping the previous buttons held. If entered correctly, you will hear another sound. Then press Start with all previous buttons held.
All Tracks
At the title screen with the phrase "Push Start Button", hold L1 + L2 + R1 + R2. If entered correctly, you will hear a sound. Immediately hold Down + X, while keeping the previous buttons held. If entered correctly, you will hear another sound. Then press Start with all previous buttons held.