The GPS system is much more sensitive to solar storms as the signal will get disrupted as it travels through the atmosphere. It would take a massive storm or burst to fry the electronics in the car - but yes, is still a concern.
I’m guessing that a driverless car doesn’t rely on GPS to stay in the proper lane - just to be able to navigate. So while it probably won’t mean a bunch of crashes, it probably would mean pulling over and stopping somewhere. (Hmm - I wonder if one can program a driverless car to “Go for a Country Drive.”)
In before the resident FR EMP deniers.