Note: In order to enable these cheats you must edit a game file. Remember to create a backup copy of this file before editing it. The file to backup and then edit is called config.cfg and is found in the gameusr folder. After backing up the file, add the following to enable the console window. 

uset g_console "1"

Now during gameplay you can press ~ to show the console window. Type one of the following codes to activate the corresponding cheat function.

Effect   :   Code

Change truck type: cheat truck <1-6> 
Super fast truck: cheat truck 7 
Change skill rating: cheat skill <1-4> 
Meet all drivers: cheat dmeet 
Get licensed route at indicated skill: cheat contracts flow <1- 4> 
Get indicated amount of money: cheat money 
Disable speeding and overweight tickets: cheat noticket.

Additionally, you can also add the lines below to the config.cfg file to to make the function keys open the corresponding menus:

Add this line to use F2 to open the Service menu: bind_imp f2 "service"
Add this line to use F3 to open the Weigh Station menu: bind_imp f3 "weightstation" 
Add this line to use F4 to open the Gas Station menu: bind_imp f4 "gasstation"