This unit will allow you to install a remote car start system on most 1998-2009 Ford, Lincoln, Mercury, and SOME Mazda vehicles equipped with Encrypted PATS passive anti-theft systems. Contact us for FREE APPLICATION ASSISTANCE. This unit requires the use of 2 working keys to be programmed. You do not have to leave any keys inside the car for this to work during remote start operation like 555u/556u/tbk3 models. This module communicates directly with vehicle databus.