Yeah, but what are you going to gain from looking at the source when you can see the screens and output directly? Is there really that much innovation in entertainment systems that can't be discerned from the UX itself, and which requires deep analysis of the code? The only way that makes sense is if the code itself gets cloned, but that's a minimal development-time savings in an otherwise huge release of software + the car itself.

DMCA in these cases seems to be a protection against third-party aftermarket for upgrades, and protection against remote hacking rather than protection of IP for competitive purposes.

Admittedly you're right; there's little to gain competitively from source access there. However, it wouldn't stop car companies from screaming bloody murder if they were required to disclose the source for those components—let alone the rest of the vehicle.

I imagine it would also create a licensing nightmare since navigation and entertainment components often utilize licensed, closed source, third party software. Much more so than the core functions of a vehicle (e.g. engine, steering, braking).

If anything, affording manufacturers the right to keep non-critical vehicle systems closed source would further the goal of opening up the critical portions.

Also, DMCA as a means of protection against remote hacking is tantamount to security through obscurity—but worse. While public source code access isn't some magic solution to security, it seems likely that it would vastly improve automotive security via allowing security researchers to do their far job more efficiently.

Good point on DMCA as not effective as a form of security through obscurity--the horse is already out of the barn before the DMCA would ever kick in.