The following are known Action Replay Codes for Mega Man Battle Network 2 on Nintendo Game Boy Advance (GBA).
These codes were also known as GameShark Codes and in most cases will work on both devices.

These codes are for the U.S. version of the game.

Master Code – Must Be On
7ebddb6c
1c7a42ff
b0e28908
90d1a2a6

Max Health
14e6ebf7
fab3790f

Max Zenny
52697379
c5a481bb

Infinite of All Sub Chips
de352b9c
9139f4a4
f55e6dca
c82cf6af

Library Complete
cc747e92
0f3af749
4eddccbf
938e4c78
001d4fcf
1e3d28f1
415bf277
7efeac16
2ea90242
44bcb6df
3487d00e
04f5118d
4fd6b714
c9cfa946
fd11f42a
c6a2ab79
dcbbda2b
e0c4fb16