Use a text editor to edit the "config.cfg" or "controls.def" file in the folder:
"\my documents\18 WoS Extreme Trucker 2\". Change the values of the following 
lines:

uset g_console "0"
uset g_developer "0" 

to: 

uset g_console "1"
uset g_developer "1" 

Then, press ~ during game play to display the console window. Enter one of the
following case-sensitive codes or key to activate the  cheat function. 
Press ~ again to close the console window.

Code              Result
------------------------
cheat heal      - restores the health of your truck and cargo (to be entered 
                  while driving if your rig gets damaged)
cheat jobs_max  - List all available jobs for current driver level (to be entered
                  during mission select screen)