From Gamefaqs
All 10 Year Raceways Open
At the title screen, put in the following code. If done correctly, you should hear a confirmation sound.
Up, Left, Down, Right, B, A, B, Right, Down
Contributed By: ATadeo, Source: Expert Gamer
All Cars
At the title screen, input:
Up, Down, Up, B, A, Left, B, B, Down
Contributed By: KasketDarkfyre, Source: Expert Gamer
Different Car Colours
To race with a different coloured car, hold L while selecting one.
Contributed By: Sprite4n, Source: Self
Increased Frame-Rate
At the title screen, put in the following code. If done correctly, you should hear a confirmation sound.
Up, A, Down, Down, Left, Right, B, B, Down
Contributed By: ATadeo, Source: Expert Gamer
Remove Backgrounds and Effects
At the title screen, press Up, A, Down, Down, Left, Right, B, B, Down. You should hear a sound.
Contributed By: Baseman, Source: Tips and Tricks
Replay options
While watching a replay of a race, press A B or C to get the in-car view. Hold down and Z and press L or R to zoom in or out.
Contributed By: Sprite4n, Source: Cheats Book
Secret Track
If you finish in first place in all ten years of Championship mde, you will get the chance to race in a secret track.
Contributed By: CChan, Source: Dreamcast Magazine
Unlock Renault Maxi Magane
To unlock this, complete Arcade mode above seventh place.
Contributed By: Sprite4n, Source: Self