Honest question: what would be the rationale to prevent farmers from repairing their machinery themselves instead of through the manufacturer (in this case, Deere)? To my mind, from the point of view of the "user" (i.e. the farmer), that can be seen as somewhat monopolistic. I tried to find similarities between this situation and that of Apple not letting users tamper with their hardware, but it could be argued that…
They're essentially creating DRM for tractor software that's so restrictive that installing new parts requires access to secret codes in the firmware in order to turn them on, then accusing farmers of breaking the law if they try to alter or figure out these secret codes in order to keep their tractor working without going to a dealer. (According to my basic understanding, correct me if I'm wrong.)