Dante's Diesel bonus level and costume
Play Dante's mission 1, then save the game. Reset the PlayStation 2 and wait for the "Press Start button" message to re-appear. Press L3, R3, L1, R1, L2, R2, L3, R3. If you entered the code correctly, you will hear a sound. Press Start to return to the main menu. Choose the "Load game" option, press L1 or R1 to access the new costume, then load a game to play the bonus level.

Lucia's Diesel bonus level and costume
Play Lucia's mission 1, then save the game. Reset the PlayStation 2 and wait for the "Press Start button" message to re-appear. Press L3, R3, L1, R1, L2, R2, L3, R3. If you entered the code correctly, you will hear a sound. Press Start to return to the main menu. Choose the "Load game" option, press L1 or R1 to access the new costume, then load a game to play the bonus level.

Dante's Diesel costume
While playing the game, press R1(2), Triangle, Square, R2(2).

Lucia's Diesel costume
While playing the game, press L1(2), Triangle, Square, L2(2).