OBDII outputs a lot of data, some of it in publically-available standard formats, but a lot of it is super seekrit codes which vary from manufacturer to manufacturer. They’ve been leaked and reverse-engineered, of course, but the manfacturers’ idea was apparently to encourage you to go to the dealer whenever the Check Engine light comes on. Some makes require not just that the underlying condition be fixed, but also require a special black box — available only to dealers and licensed service providers — just to turn off the idiot light.
This openness by an automaker to hacking their software is pretty much unprecedented afaik. Hopefully it’s not just lip service. I’ve never been a Ford guy but between this and them not needing bailout money they’re starting to look pretty good.