Head to the Extras menu and select the Cheats option to find a prompt to Add Cheats. You can enter the codes below for the corresponding effects, but note that auto-save and Achievements or Trophies are disabled while they are in play.

Code	Effect
bigheadmode	Big Head Mode.
cheese	Instant cash ($100,000).
clearskies	Clear skies.
evilcars	Evil cars.
fastforward	Faster Time.
fryhole	floating corpses.
goldengun	One-hit kills.
goodygoody	Notoriety eliminated.
heavyrain	Raining heavily.
insanecity	Insane city.
isquishyou	Vehicles crumple.
letsrock	All weapons.
lightrain	Raining lightly.
notrated	Kills produce blood explosions.
overcast	Cloudy.
repaircar	Repair vehicle.
runfast	Unlimited sprinting.
unlockitall	Everything unlocked.
vroom	No vehicle damage.