Auto sprint is a misnomer, the other shops started calling it auto sprint so we did too, now I think they call it something else and I'm too lazy to change the documentation. In any case, with auto sprint on, you have to flick your aim key (usually left trigger) and push forward on the stick and your guy will start sprinting. Basically instead of pushing LS (left stick) you will be pushing LT (left trigger) to sprint. It should really be balled sprint-button-reassigned-to-left-trigger-mod instead of auto sprint or auto run.
I have to call it that or else people who see that the competition have something called "auto sprint" panic when I don't show "auto sprint" in my list of features on the website.