Kai, in my example where a sensor may be connected to the engine, it is unwise to have other ground paths apart from the earth strap for the engine itself. The sensor itself floats electrically. In this instance, what do you you connect the shield to? Our friends at compliance club do make mention of certain instances where earthing both ends of the cable is verboten. They also suggest one uses only one ground plane on the pcb rather than separating analog and digital planes.

As for the reliability of automotive electronics - things have come a long way since the dodgy ignition coils in Trabants!