Unfortunately, the correct answer to your question is MAYBE. There are many factors which come into play in determining whether the second trust deed holder can come after you for the monies owed, not the least of which is that many HELOC loans contain personal guarantees.
The good news is, if you are doing a short sale, this item becomes part of the negotiation. Make sure that you list your home with an experienced Short Sale Listing Agent. They will negotiate on your behalf to get the second mortgage holder to put wording in their acceptance of the short sale to protect you from owing additional money after the short sale. There are no guarantees. Many lenders are asking for either some money at closing or an unsecured note for part of the deficiency. It is all in the negotiations and how firmly you and your Realtor stand your ground. Remember, the bank does not want to own your home (this creates more issues for them than you or I even know), they want their money.
A good Realtor, in conjunction with your tax professional and perhaps with the additional assistance of a one hour consultation with a good real estate attorney, will help you make an informed decision on what is best for you. It all starts with your decision to move forward and with your choice of who to have on your team in this very sensitive, often difficult, and definitely long process.
I wish you much success in getting this chapter behind you and moving on with your life. Dare to Dream.
Real Estate Consultant
RE/MAX Palos Verdes Realty