Typically you will need an order of removal which you can obtain from the court. in Harris County this is an informal process and is handled through the probation liaison officer.
My answer is based upon the limited amount of information available at the time of writing.I am a Texas DWI Lawyer. If possible, hire an attorney who is a member of the National College of DUI Defense, who is familiar with your jurisdiction. Jim Butler- myhoustondwi.com, dwisurcharge.com 713-236-8744
If you don't have a good relationship with your probation officer, I would suggest getting an attorney to help you have this lifted or removed.
The specifics of your case will determine how long you are statutorily required to have the interlock on your car. But the judge can require the interlock beyond what the statute requires, if they feel it is necessary.