After starting a game or loading an existing game go to the "Campaign", "Bonus", and "Options" screen and input the following. The Screen will flash if you put the code in correctly.

Infinite Health:
Press: left,left,up,left,right,down,right

Infinite Ammo/no reload/rapid fire:
Press: up,down,left,right,up,up,down

All Missions completed: (using this code before you finish the game will unlock all mission as being completed. Do not use it if you are in the middle of a mission.)

Press: down,up,left,right,right,right,up,down

Bonus Cybertron missions: (this code will do the same thing as in the missions code. It will show as completed.)

Press: right,up,up,down,right,left,left

No Traffic/police/military: (this code will only let the rival transformers you are battling drive around the streets)

Press: right,left,right,left,right,left,right

Play as "Optimus Prime" generation one version: (using the gen1 skin code of the characters decreases your weapons power from the new versions)

Press: down,right,left,up,down,down,left

Robovision Optimus Prime:
Press: down,down,up,up,right,right,right,

Starscream Gen 1:
Press: right,down,left,left,down,up,up,

Jazz Gen 1:
Press: left,up,down,down,left,up,right,

Megatron Gen 1:
Press: down,left,left,down,right,right,up,

Unlock Unlimited Health:
Press Left, Left, Up, Left, Right, Down, Right.

PS:
Cheats are the the same for this on ps3!

At the main menu press the following buttons for each cheat

Unlock all missions
Down,up,left,righ,right,right,up,down

Infinite Ammo

Up,down,left,right,up,up,down

Complete the Autobot Section of the Campain Mode to get the level titled Cybertron: Autobot