Master code:
Press Up(3), Left, Right, Circle, Triangle at the main menu to unlock all cheat options.
Hardcore realism mode:
Press Up, Down, Left, Right, R, Up, Down at the main menu. Alternately, get a 100 point rating on a track to unlock the hardcore realism mode option for that track.

Arcade-style beat the heat mode:
Press Up, Down, Left, Right, R, Down, Up at the main menu. Cars can now hit the wall in beat the heat mode.

Shoot paintballs:
Select single race or head-to-head mode. Press Up, Down, Left, Right, R, Up(2) at the "Race Day" screen. Use your horn (press Up) to shoot a paintball. Alternately, select practice mode and press Up, Down, Left, Right, R, Down(2) to enable paintballs.

Remove replay text:
Press Up, Down, Left, Right, R, Down, Up at the main menu.

Beat the heat mode skip:
Press Up, Down, Left, Right, R, Ri! ght, Left at the main menu. Repeat this code to advance to the next level.

View credits:
Press Up, Down, Left, Right, R, Up(2) at the main menu.

Richard Petty:
Successfully complete all Heat challenges with a bronze or higher rating.