The following are known Action Replay Codes for Carmageddon 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 Credits
0199b5c3
0199b6c3
0199b7c3

Infinite Health
016fa8c3

Stop Timer
0199a6c3