While playing a game, press Q + I + [F12] while in a truck. Press ~ to display 
the console prompt in the lower left part of the screen. Enter one of the 
following codes, then press [Enter] to activate the corresponding cheat 
function:

Result - Cheat Code
All modes unlocked - freeman() 
No truck damage - ironman(1) 
Repair truck - hanyman() 
Set tire size - settyrescale([number])