Yeah, I tried looking up the Codes already made, and that did not help, since those are basically Assembly or something close to it.
@Retroboy - Could be another option to go for instead of the PC Version
these work when i activate them
Grand Theft Auto 3 Cheats for PS2
Cheat Code Effect
R2, R2, L1, R2, Left, Down, Right, Up, Left, Down, Right, Up Unlock all weapons
R2, R2, L1, L2, Left, Down, Right, Up, Left, Down, Right, Up Get full armor
R2, R2, L1, R1, Left, Down, Right, Up, Left, Down, Right, Up Regain full health
L2, R2, L1, R1, L2, R2, Triangle, Square, Circle, Triangle, L2, L1 Blow up all cars
L1, L2, R1, R2, R2, R1, L2, Triangle Clear the weather
L1, L2, R1, R2, R2, R1, L2, Square Make cloudy weather
L1, L2, R1, R2, R2, R1, L2, X Make foggy weather
L1, L2, R1, R2, R2, R1, L2, Circle Make rainy weather
R2, R1, Triangle, X, L2, L1, Up, Down Crazy pedestrians
Down, Up, Left, Up, X, R1, R2, L2, L1 Cause a riot
Triangle, Up, Right, Down, Square, R1, R2 Slow motion gameplay
Triangle, Up, Right, Down, Square, L1, L2 Fast motion gameplay
Circle, Circle, Circle, Square, Square, Square, Square, Square, L1, Triangle, Circle, Triangle Speed up time
Right, R2, Circle, R1, L2, Down, L1, R1 Flying cars
Circle, Circle, Circle, Circle, Circle, Circle, R1, L2, L1, Triangle, Circle, Triangle Spawn a tank
R1, L1, R2, L1, Left, R1, R1, Triangle Better driving skills
L1, L1, Square, R2, Triangle, L1, Triangle Invisible cars
R2, R2, L1, R2, Left, Right, Left, Right, Left, Right Higher wanted level
R2, R2, L1, R2, Up, Down, Up, Down, Up, Down Lower wanted level
R2, R2, L1, L1, Left, Down, Right, Up, Left, Down, Right, Up More money ($250,000)
Square, L1, Circle, Down, L1, R1, Triangle, Right, L1, X More gore
Down, Up, Left, Up, X, R1, R2, L1, L2 Make pedestrians attack you
Down, Up, Left, Up, X, R1, R2, L2, L1 Make pedestrians fight each other
Right, Down, Left, Up, L1, L2, Up, Left, Down, Right Unlock all outfits