At the main menu (where you choose map select, vehicle select, etc.) type ENABLE quickly. You'll gain access to all the tracks and cars. Start a race and press F4 until the words CHEAT MODE appears. You may now enter any of the codes below.

Code EffectF5 Repair all damageF6 Toggle InvulnerabilityF7 Add 30 seconds to the timerF8 Freeze/Unfreeze timerF10 Increase lap counterF11 Gain 5000 creditsF12 Switch between each opponent's camera and your own. External view only.SHIFT-F6 Show opponents on mapSHIFT-F7 Adds 300 seconds to timerSHIFT-F8 Toggle shadows (none, your car, all cars)SHIFT-F10 Increment checkpoint counter SHIFT-F11 Lose 5000 creditsCTRL-F8 Toggle shadow mode (solid or translucent)CTRL-KEYPAD 1 Toggle flight. Use normal movement keys to fly. Press Keypad 5 to land, and Keypad 9 or Keypad 6 to change your pitch.