O'Brien was charged two days after pedestrian Jim Reed, 43, was found on a street near the bishop's home. O'Brien later resigned and told police he didn't realize he struck a person.
He did not comment during or after his arraignment in Maricopa County Superior Court (search) on Monday.
Prosecutors have said that O'Brien was not impaired by alcohol at the time of the June 14 crash. If he had stopped right after the collision, he likely would not have faced charges at all, County Attorney Rick Romley has said.
Instead, investigators used witness testimony to track the car involved in the fatal accident to the diocese and then to O'Brien.
Reed was crossing in the middle of a block after dark, and tests revealed he was drunk.
O'Brien is free on $45,000 bond. He has been charged with leaving the scene of a fatal accident.
Earlier, O'Brien cut a deal with prosecutors in which he admitted he sheltered accused sexual molesters in the clergy and promised to relinquish some control of the diocese. The deal allowed him to avoid an obstruction of justice charge.