If your not a State or Federal Agency, then you would need to file a lawsuit, win a judgment, and file a Motion for Garnishment with the courts, and typically you must know the information of what you are seeking to garnish.
Sue the individual in the appropriate court and if you prevail you will receive a judgment writ. You then file the writ with the court clerk as a wage garnishment and have the garnishment order...
In the State of Texas, the answer would be "YES" as both parties signed for the car loan and both are responsible for the balance due. I was the primary signor but the cosigner had the car and was...