if your on PS2 (which i assume you are) Try these: Each of the weapons codes give you extra money

Full health

While playing the game, press R1, R2, L1, Circle, Left, Down, Right, Up, Left, Down, Right, Up. If you entered the code correctly, a message will appear. Note: If this code is enabled when there is damage on your car, the meter will be reset to zero without changing the visible effects of the damage.

Armor

While playing the game, press R1, R2, L1, X, Left, Down, Right, Up, Left, Down, Right, Up. If you entered the code correctly, a message will appear.

Weapons (tier 1)

While playing the game, press R1, R2, L1, R2, Left, Down, Right, Up, Left, Down, Right, Up. If you entered the code correctly, a message will appear. The least powerful weapons in each category will be unlocked.

Weapons (tier 2)

While playing the game, press R1, R2, L1, R2, Left, Down, Right, Up, Left, Down(2), Left. If you entered the code correctly, a message will appear.

Weapons (tier 3)

While playing the game, press R1, R2, L1, R2, Left, Down, Right, Up, Left, Down(3). If you entered the code correctly, a message will appear.

Raise wanted level

While playing the game, press R1(2), Circle, R2, Left, Right, Left, Right, Left, Right. If you entered the code correctly, a message will appear.

Lower wanted level

While playing the game, press R1(2), Circle, R2, Up, Down, Up, Down, Up, Down. If you entered the code correctly, a message will appear.