Enter the Goals/Notes/Images screen (press Select) and then enter the following code:
L2, R2, L1, R1, Start, Start, Start
This will open a new folder in which you can activate God Mode, Full Health, Full Energy, Full Ammo, Full Mods, All Skills, Full Credits, Tantalus.
Note: After new level area loads, you may need to re-toggle the God mode option.