varjag parent
As long as it exchanges information (mundane things like muting the music when parking sensors have to be heard, requesting battery/fuel status for advising the next fill stop etc) the isolation can't be entirely complete.
How about read only over an optic cable?
I wasn't really talking about galvanic isolation. And on modern vehicles instruments and infotainment tend to run hypervised on the same physical host. Thing is as long as you exchange information there's always potential for logic coupling allowing the trouble to cross the boundary. Not to mention the basic rate excess/denial of service situations.