The results of the written and oral portions of the preliminary exam are reported to the entire faculty of the department and the entire faculty makes the final decision on whether you pass or fail the exam.
If you take the exam for the first time but you do not pass outright, you will be given one of 2 options by the faculty:
You will be informed by a letter to your home address of the decision of the faculty. You may also ask your advisor what the decision was.