This issue is only confusing to the extent this isn't considered.
>an algorithm is just another car part
Exactly. And the designer is on the hook for negligence in the usual way - but not for malicious, tragic, and/or unforseeable circumstances that may lead to death or injury.
Finding the boundary between those will keep a lot of lawyers very busy. But I don't think we need to start assigning personhood and agency to a steering system just yet.
A corporation is a legal person, which makes it a lot easier to enter a contract with one, but that doesn't imply it has rights. You can own a corporation without it being slavery.
It's still an abstraction over something akin to mechanical failure, like how corporate personhood is an abstraction over a group of people. It doesn't mean the algorithm has rights, any more than a fuel injection pump does. You also can't murder a corporation, even though it's a legal person.
If the purpose is to account for freak events where the algo misbehaves for reasons that couldn't be foreseen, is that any different than a (non-autonomous) vehicle part failing despite being well-designed and maintained? This is not a new situation - an algorithm is just another car part. You don't need to give legal personality to the fuel injection pumps or the steering column in case it fails unexpectedly.