As I am not licensed in your jurisdiction, I can only provide general information. Due to the severity of any DUI offense, I would strongly recommend consulting an experienced DUI attorney licensed in your jurisdiction. In Illinois, drivers operating under the influence of alcohol for a second time can receive a sentence of imprisonment, mandatory suspension of license (for at least one year) as well as significant fines.
Because state laws regarding DUI vary, contacting a local lawyer experienced in DUI law for your state can provide more relevant information.
If you are convicted of a DWI-2nd in Texas, some jail time is mandatory even if you get probation and the minimum term of confinement for a DWI-2nd if you don't do probation is 30 days. Some counties allow you to satisfy this time in jail through work-release, weekend incarceration, or weekend work programs. A third DWI would be charged as a 3rd degree felony carrying up to 10 years.
Having the PI also makes your DWI case more complicated. Some prosecutors may look at your case and think that you have a serious problem with alcohol and that in order to protect the public you need to do a lot of jail time. That's why it's important for you to hire a local criminal defense attorney as soon as possible to protect yourself and do as much as you can to show that this doesn't happen again.
Disclaimer: This answer is provided as a public service and as a general response to a general question, it is not meant, and should not be relied upon as specific legal advice, nor does it create an attorney-client relationship.
There are a lot of facts that may change the length of time spent in jail, but a s a general practice the ADA's in Harris County will be asking for jail time. If you are still on probation from your first DWI, it's guaranteed, they will seek jail time. Just because the ADA's seek jail time does not mean that you will actually spend time in jail. A top notch DWI lawyer will help you avoid this at all cost. And good lawyers don't start thinking about a plea first. A plea is the last thing a good lawyer will try AFTER reviewing the facts of the case and investigating the entire case. Maybe you have a valid defense, or the officer did not have probable cause to stop you or for any one of a hundred other reasons, you may not be guilty. Only a quality DWI lawyer will be able to dig into a case and give you the answers. Your best bet is to make an appointment with a few good lawyers and hire one to represent you. You wouldn't perform brain surgery on yourself after getting a book from a neurosurgeon neighbor. Practicing law is no different. You can't do it and decide on any defenses without knowing what a lawyer knows. Good luck!
The punishment range for DWI 2nd is 30 days in jail up to 180 days in jail, and up to a 4000 fine. However, the jail time can be "probated," which means you get probation. However, even if you get probation, by law you must serve at least 3 days in jail as a condition of probation. If your prior DWI was within 5 years, it is at least 5 days in jail. Jail as a condition of probation can be as many as 30 days.