Doom 3 Xbox Cheats

do you guys know where to find Doom 3 Xbox Cheats.i just rented it and it is a very awesome game but it is difficult and i need some cheats.i found one but i cant get it to work here it is.

Infinit Ammo
First throw all your bullets then press and hold R, L then press x,b,b,x,y,y,y,a,a,x,x,a,y,b,x and you will have infinite ammo
submitted by: Alvaro Vazquez

http://www.gamefaqs.com/console/xbox/code/914444.html

Has plenty of cheats for Doom 3 (X-BOX).