That's not news from GM...My burb has 5 computer systems linked by an onboard LAN...there is the PCM that controls the engine, the TCM that controls the transmission, the BCM that controls lighting, entertainment and such, the ABS module, and the Ride Control Module that varies voltage to the real-time damping shock absorbers.
Stuff that is "emissions-related" under OBD II has to be accessible by any shop, but in this case stuff related to ABC, RCC and part of the BCM is only diagnosable using the official GM Tech II scanner, a $4000 tool.
As new vehicles get more sophisticated and more integrated, the amount of code that the mfr needs to write to control all of the functions has grown exponentially. I get that the OEMs want to protect their intellectual capital, but the idea of owning a vehicle that you can't fix yourself is going to be a hard sell.....especially a tractor for gosh sake.
