Based on the search results, it appears that car dealerships hours of operation on Sundays vary depending on the state. In New Jersey, for example, car dealerships are not open on Sundays due to a state law that restricts or bans car sales on Sundays. This law is part of a set of laws called Blue Laws, which were originally intended to enforce religious standards and restricted certain activities during times where people were expected to attend church services. Other states, such as Maryland, Michigan, Nevada, North Carolina, Rhode Island, Texas, and Utah, allow car dealerships to be open on Sundays, but with limited sales hours. However, even if a car dealership is open on a Sunday, it may be difficult to complete a car transaction since many of the supporting entities, such as insurance agencies and the Department of Motor Vehicles, are closed.

In summary, whether or not car dealerships are open on Sundays depends on the state, and even if they are open, it may be difficult to complete a car transaction due to the closure of supporting entities.