Originally Posted by MPHS_AGM
Looking through the GM service manual for the 2013 and found a note that may solve the HSA problem. There is a note that says the hill start assist feature will not operate if the stability control is disabled.
It is raining here so I am not going to go and test this until Sunday or Monday. If you get a chance to test this, please report back!
This doesn't work on my car. I tried PTM Mode 5 in my driveway today and HSA was still active.