PS3 Grand Theft Auto IV cheats are available at most major game walkthrough sites, including GameFAQs, IGN and Cheat Code Central. Input codes by opening Niko's cell phone and manually inputting the number code for the desired cheat. In most cases, this saves the number under the Cheats folder in Niko's cell phone.
Cheat codes for other games are also available on the websites. GameFAQs allows user contributions, while other sites, such as IGN, have the codes submitted and verified by their staff. Some cheat codes may cause instability in the game, which is why CheatCC recommends saving before inputting the code, not after. However, it mentions vehicle exploits that are only possible by saving after a cheat is activated and is loading back.
In GTA IV, inputting cheat codes may disable some related achievements. The phone number cheats are largely shared between PC, Xbox 360, and PS3 versions of the game. Some vehicle cheats only work if the player has the appropriate DLC expansions installed, namely "The Ballad Of Gay Tony" and "The Lost And The Damned." Some advantages that are sometimes referred to as cheats, such as unique weapons and unlimited ammo, are actually unlocked by completing objectives within the game.