Cheat mode:
Enter one of the following codes to unlock the corresponding car in Grid World and Raceday. Note: You must have 40,000 in funds to start your own team to get the option to view and test drive the bonus cars.
Buchbinder BMW 320si vinyl
Enter F93857372 as a code.
GameStation BMW 320si vinyl
Enter G29782655 as a code.
Stage 1 classic muscle cars
Enter MUS59279 as a code.
MicroMania Paganini Zonda vinyl
Enter M38572343 as a code.
billi no mates
Play.com Aston Martin DBR9 vinyl
Enter P47203845 as a code.
Tuner cars
Enter TUN58396 as a code.
Disable Opponents:
Go to your Grid Folder and then the AI folder. Remove the file \\\ "ai_vehicle_config \\\". If you start a race, the opponents stay and you can enjoy the race. Make a backup of this file before removing so you can restore the game's original functionality.