Things You'll Need
Instructions
Insert your Pokemon HeartGold game into your Action Replay DS cartridge. Put the cartridges into your Nintendo DS and turn it on. Tap the "star" icon on the bottom screen and scroll through the games list to find Pokemon HeartGold. Check both game name and ID before continuing.
Enter the "Wild Pokemon Modifier" code "94000130 FCFF0000 62111880 00000000 B2111880 00000000 00000D14 01ED0001 00000D18 00640002 94000130 FDFF0000 62111880 00000000 B2111880 00000000 DA000000 00000D16 C0000000 00000027 D7000000 00025A68 94000130 FDFF0000 62111880 00000000 B2111880 00000000 DB000000 00000D1A C0000000 0000000B D8000000 00025A5C D2000000 00000000." Double-check your code before naming it. Save your code and tap the "Start" button on the bottom screen.
Select your game save, waiting for the game to resume. Press the "L" and "R" buttons to activate the code; check your "Items" pocket to find 493 Master Balls. Discard the appropriate amount of Master Balls until you reach your desired Pokemon's "National Pokedex" number. Your chosen Pokemon appears in wild Pokemon encounters after the code activates. Hold "L" button to activate the code again after exiting the menu; enter a patch of grass to encounter your chosen Pokemon.