No, if you are merely a little late in returning the car but have made clear your intention to return (hopefully, you have faxed, emailed, and/or texted--i.e. created a written record, whose delivery you can prove so long as you had the right email address, fax or cellphone number, etc.), you should not be arrested for that. Criminal charges are based on there being criminal intent--it's why, for example, if I walk out of a store with something I did not pay for and knew I had not paid for, that is shoplifting, since I had the intent to steal; but if I accidently pick up someone's coat from a coat room at a restaurant because it looked like my coat, that is not theft, since in this case, it was a mistake, not an intent to steal. So if you can show that you are intending on bringing the car back at the first reasonable opportunity, you have not commiitted a crime.