Can the dealership charge you with auto theft if you are in default on your payments?

Not if you are on the title to the vehicle and own it. Whoever holds the loan on the vehicle can repossess the car however if you are late with payments. Contact the lender and work something out. You do not want your car repossess. Credit will be ruined for 7 years, and you will still have to pay the repo fees plus the difference in the balance on the note and what the car brings when they sell it.