Q: So I need a special tool to remove a knock sensor on a 2005 Buick LaCrosse

An ordinary 6 point socket is used to replace the knock sensor on this model. Stalling, if that is what you mean by "cutting off", is not typically caused by a faulty knock sensor. Unless the knock sensor has been directly tested (using an oscilloscope or automotive scope) and tests bad, it should not be replaced. Instead, if you are having engine operating problems, you should request an engine diagnostic so that a certified mechanic can conclusively pinpoint the underlying fault(s) and get those repaired for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic because we want you to make the most of your repair dollars and help you to get the best possible results.