My daughter died in Arizona, intestate, unmarried with no children. Her estate is insolvent. How do I proceed?

I would suggest taking the time to discuss your situation in more detail with an Arizona attorney, even if it is just paying for a 1 hour telephonic consult. From the limited information you have provided, it sounds like you have no obligation to start up a probate, and can just walk away.

Without descendants or spouse, the parents are equal heirs of the estate. You can probably transfer the car to yourself, using a small estate transfer process. You will be potentially liable to creditors of the estate for 2 years from the date of death for the value of all property transferred to you. If no creditor files a probate during that time, their claim lapses or expires.