it's not paranoia chips with backdoors which would allow exactly something like that (or many other things) have been found more then once in recent years AFIK

it's not paranoia chips with backdoors which would allow exactly something like that (or many other things) have been found more then once in recent years AFIK through a fancy personal car stopping working is the least relevant target. Network backbone, smart phones, and other core infrastructure is a much more relevant target. And even for cars all the non-personal vehicles (e.g. ambulance, trucks, police ...) are much more relevant targets.