[glurgh]

It's not really 'autonomous driving' so you might be overestimating the safety factor implied by the term 'autopilot'.

I'm not a car person or expert in the field but I've done a little bit of work on automotive systems. As the other responders pointed out these systems are designed to, ECC or not, do things like (at the slightest sign of inconsistency or error)

- reset and recover very quickly

- enter reduced functionality or failsafe modes

- fully disable themselves and anything that might cause you to rely on them

They're fundamentally built around the eventuality of them failing and with consideration of the things that need to happen when they fail. They don't usually rely on 'well, we'll just put in a somewhat more reliable component'.