How to Unlock Halo's Warthog in Forza 4
Even though you can't drive it inForza 4, you can, however, viewa Warthog from Halo in the game's Autovista mode. If you really want to get this vehicle unlocked as soon as you can, then there is a way on how you can do it.
First off, know what Autovista mode is. Autovista is a feature of Forza 4 where you can view the details of the game's assortment of beautiful cars. You can walk around the car, pop the hood, get in, get out, get back in and even turn the key (or push the button). It's almost like being at a dealership, only without the pushy salesman telling you about their $5000 cash-back special (without mentioning the only color available for every car in their stock is Banana Yellow).
In order to access and see the Warthog, you have to unlock every other car in Autovista mode. There is no need to panic, as it's an easy process to accomplish, thanks to our friends at Kotaku.
When you first get the game, you will have Autovista access to about six cars. In order to unlock other cars in that mode, you need to pass a few challenges. The first challenge is driving around in a car (any car in question) for over a lap or two, followed by the challenge of passing over a number of cars in an actual race.
After you've done all of that, you have to complete in twenty races before you unlockthe Warthog. You should note, that you only have to unlock the cars that come standard with the game. Thus meaning the 2012BMW M5 that's marked as DLC isn't required, despite it will be free to unlock at launch. After all that, you now have the Warthog to gaze upon and wish you could drive in the game.