Activating "Unlock All Cars" alongside a "Profile Fixer" code can corrupt your save file or cause the game to freeze at the Start Screen. Try enabling only one code at a time to isolate conflicts.
Gecko codes are region-specific. A code written for the US version won't work on a PAL disc, and vice versa. The collection above is verified for the US version (typically identified by a game ID starting with "GNFE"). If you're using a different region, look for codes specifically marked for that release.
Keep the police off your back entirely, or reset your heat level instantly. 042A5E04 00000000 Unlock All Cars
These codes are frequently used to expand the base GameCube experience: Unlock Black Edition
: Gecko codes can handle complex instructions, such as changing how individual car physics behave. How to Make Gecko Codes Work