It could be some other sensor besides the throttle body. What ever it is, it is making the drive by wire close the throttle. It most likely is the throttle position sensor or the wiring that connects it to the computer or the input ciruit on the computer board. First thing to do is check that all the electrical connectors on the throttle body are properly connected. It they are, it is going to require connecting the car to an OBDII diagnostic machine and running through the whole diagnostic tree. Most likely the best thing to do is take it to a dealer.