The following are known Action Replay Codes for Mega Man Battle Network 4: Blue Moon on Nintendo Game Boy Advance (GBA).
These are Action Replay Version 3 (V3) Codes.
The codes should work with the region specified but may work for other regions as well.
(M)
a7e4a2ca
7d29f307
574fbd83...
action replay
blue moon
cheat codes
cheats
chips
codes
custom gauge
damage
enhancements
exploits
game hacks
game modifications
gametweaksgameboy advance
health
mega man battle network 4
region
secret codes
unlockables
version 3