The following cheats may disable your game achievements! So I suggest that you either complete the achievement first or just do not save your game after you enter any of these cheat codes.

GTA 4 Cell Phone Codes
Enter these GTA 4 cheat codes in the game with Niko Bellic’s phone. While you are in game play, press UP to see the phone then press UP again to see a keypad to enter the following cheat codes. When you enter the code correctly, you will see a “cheats menu” option appear underneath “Options”. You can access your cheats here without having to enter them into the phone again.

Full Health:
Call 362-555-0100

Restore Full Health and Ammunition:
This code blocks the “Cleaned the mean streets” achievement!
Call 482-555-0100

Reset your Wanted Level:
This blocks the “Walked free” achievement!
Call 267-555-0100

Increase your Wanted Level Up One:
Adds a star to Niko’s wanted level.
Call 267-555-0150

Weapons 1:
Handgun, Shotgun, MP5, M4, Sniper Rifle, RPG, Grenades, Baseball bat.
Call 486-555-0100

Weapons 2:
Call 486-555-0150

Change the Weather and Brightness:
Call 468-555-0100

Spawn Annihilator (Police Helicopter):
Call 359-555-0100

Spawn Cognoscenti:
Call 227-555-0142

Spawn Comet:
Call 227-555-0175

Spawn FBI Buffalo:
Call 227-555-0100

Spawn Jetmax:
Call 938-555-0100

Spawn NRG-900:
Call 625-555-0100

Spawn Sanchez:
Call 625-555-0150

Spawn SuperGT:
Call 227-555-0168

Spawn Turismo:
Call 227-555-0147