If they distribute a copy of the source at the same time they send you the binaries (in this case, the car) - then they have no further obligation to distribute the code. They don't have to maintain an online repository, nor worry about who is entitled to what version of the code.
Under GPL, you are only entitled to the source of the binaries you are given.
Under GPL, you are only entitled to the source of the binaries you are given.