5G won't fix anything. The location precision is worse than what you can usually get with the latest GNSS receivers. And what happens when the 5G tower is down because a construction crew accidentally cut the backhaul fiber?
Apropos of anything else, the tower knows where it is, unless it's mobile. Having no backhaul doesn't mean it can't be broadcasting / used for location information. They also (almost) always come with their own battery backup / generator.
I assume the cars would stop and we would have to go back to driving them manually for a few hours or days