The following are known Action Replay Codes for Karate Joe on Nintendo Game Boy / Color (GB / GBC). These codes were also known as GameShark Codes and in most cases will work on both devices.

Device Compatibility: Action Replay & GameShark

Infinite Health
910526d0

Infinite Lives
910914c3

Max Score
910924c3
910925c3
910926c3
910927c3
910928c3
910929c3
91092ac3

Max Level
91094bc3