You mean the power steering motor? That's used for, well, power steering. There's no separate autopilot motor AFAIK.
Honestly, I'm not 100% sure. I haven't dissected an autopilot equipped vehicle yet. Would seem odd to me that the normal power steering motor would be able to precisely hold and control the steering on its own based on digital commands. If it can then I've been misinformed. *shrugs*
The feel of the steering while using auto steer is definitely different than even a car without power steering. You can feel the system holding the wheel where it wants it with enough force to keep it there. Power steering assist isn't used to hold the wheel, rather to make the wheels easier to turn. I guess it could be used in this capacity, but in that case I wonder if they couldn't implement some kind of manual activation auto parallel parking feature on the "classic" Model S (with parking sensors)?
In any case, I don't expect them to do anything to correct the issue or to do anything at all about the ridiculous delay of the release... which I guess is the problem and something people should be aware of.
Summary: Autopilot was announced as if it was already available (and was portrayed this way on their website for a full year). The P85D doesn't have more range than the P85. The P85D barely has more horsepower than the P85 (not "50% more" as claimed). The free software update to make the P85D perform better turned into a $5,000... er, $7,500 hardware update that is still yet to materialize. I've yet to see independent confirmation that the P90D can achieve a 10.9 second quarter mile time as claimed.
I could go on, but basically if I've learned anything from this whole experience with the P85D it's simply that Tesla can not be trusted to honestly portray anything anymore. And you know what? That's a sad place for them to be in the eyes of some of their most loyal customers and it's going to bite them in the *** sooner or later.