Action replay codes are only available for select games. There is never going to be a Dragon-Ball z legacy of Goku 3 but there is Dragon-Ball Z Buu's Fury which is basically what happens after.

Dragon Ball Z The Legacy Of Goku 2

Dragon Ball Z Legacy Of Goku 1 Cheat Codes

Dragon Ball Z Legacy Of Goku Action Replay Codes 1

True to the DBZ series, created by Akira Toriyama, the Legacy of Goku II follows events from the Trunks Saga until the completion of the Cell Games. After the death of Gohan, assassinated by Androids 17 & 18, Trunks has no other choice but to go back in time, 16 years ago, to change the course of history. You will begin to assume the role of young Gohan before taking control of Piccolo, Trunks, Vegeta and Goku himself. Epic fights await you against tough opponents such as Dr. Gero, Androids 17, 18, 19 and of course Cell.
Released in 2003 on the Game Boy Advance (Nintendo), this fighting RPG game features 20+ hours of gameplay and can be played here online.
Game Controls:
Enter: Start
Bkspace: Select
Arrows: Move
Z: Button A
X: Button B
A: Button L
S: Button R
See also:
Dragon Ball Z: The Legacy of Goku 1
Dragon Ball Z: Buu's Fury