ATV Offroad Fury 4 (PS2)

ATV Offroad Fury 4 cheats:

75,000 credits
Select options at the main menu. Click on player profile, and click the "Cheats" option. Enter the following.

All Sponsors
To unlock all in-game sponsors, head to the cheat screen and put in (case-sensitive) uDunGud as a password.

All Tracks
To unlock all of the game's tracks, simply type in the cheat "TraxAhoy" on the cheats menu.

Chimera
Finish P2P with the truck on expert difficulty.

Fast Easy Back Flips/Frunt Flips
This isnt exactly a cheat but if you ever try to pull off the back flip or frunt flip they always take a long time to rotate well if you double tap the direction of the flip it will go twice as fast then you can pull off a double or triple back flip.

Fireball
Finish the P2P with bike on expert difficulty.

Fresh Treds
Head to the in-game cheats menu and type in "newtreds" (minus the quotes) for some fresh treds on your vehicle.

Other Sites you may consider
CheatServer.Com
Cheat Codes Club