You don't need it but it allows you to change some of the vehicles electronically controlled parameters. It's free software! The only other thing required is an OBDII adapter which can be found starting at $25. With it I was able to add NAV to my 2014 and 2015 FiST. I was able to change parameters to engage Daytime Running Lights in my car. I enabled a reverse gear sound but will likely go back in and turn that off. I enabled the foglights on with low or high beams but haven't confirmed that my settings are correct yet. You would be surprised at all the things it allows you to do. When I'm ready I will upgrade from Sync2 to Sync3 and the Forscan software will allow me to configure the APIM so that my vehicle thinks it is As-built otherwise it wouldn't work. I hope those examples help you to understand all that it can do and peak your curiosity to learn more. Sorry I couldn't be more extensive in my earlier response but I was spending time with my wife on my day off. Happy wife, happy life and I still enjoy being with her. Lol
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