In most states, the sentence for your first DUI offense will involve a license suspension that lasts between six months and one year, a slew of fines and fees, and a term of informal probation. Depending upon the severity of your offense and the specifics of your state's DUI statutes, this term of probation may last from three to five years. If you caused serious injury or significant property damage during the incident that led to your DUI arrest, you may be placed on a longer term of supervised "formal" probation.
Regardless of its exact requirements, the state views your probation as an explicit agreement between you and your sentencing judge. If you violate any of its terms, you'll be subject to serious penalties that may include the reinstatement of your original sentence. With few exceptions, judges have little sympathy for probation violators. As such, you should prepare yourself to spend some time in jail.
There are several factors that will determine the extent to which you'll be punished for your new offense. First, you'll need to plead guilty to the new charge unless you can prove beyond a shadow of a doubt that your arresting officer made a mistake. These days, this is difficult to do: Most police departments now use dashboard cameras to back up their officers' assertions. Even if you choose to accept the new charges, you'll want to hire a criminal defense lawyer to negotiate a more favorable sentence.
The circumstances surrounding your illegal drive are also important. If you can prove that you were driving on a suspended license to respond to a serious, time-sensitive emergency, your sentencing judge may be inclined to show some leniency. Lest you come off as petulant, you'll have to make a powerful case that the circumstances warranted your decision to break the law. In the past, life-or-death dashes to the hospital have been among the only events that invite sympathy from the court.
Assuming that you're convicted of violating your probation by driving on a suspended license, you'll be subject to several penalties. For starters, your license suspension will likely be suspended for a period of a year or more. Unlike your first offense, this second conviction may disqualify you from receiving any restricted-license privileges. You'll also be hit with additional fines that may approach $2,000 and could be thrown in prison for up to a year.