To enter each code, go to the 'Bonus' section of the game's options and enter the code you are given into the 'Enter Bonus Code' section.
Complete the entry by selecting the return icon at the end of the list of letters. The codes are activated when a tick appears next to them in the 'Activate Bonus' section.
Enter "DBXLMNAN" to unlock all the cars and championships except the last 3 bonus Championships
Enter "LLNWQCKO" to unlock the 3 special bonus Championships and all the cars
Enter "NYOOKJKW" to double the available engine power for all cars, including the AI cars (XBOX) or to increase the overall speed of your car (PC)
Enter "REGOCNYO" to swap Frontwheel drive cars to rear wheel drive and vice versa
Enter "URPPSHYI" to make the cars undamagable
Enter "PDICULGR" to unlock all the cutscenes