There's no standard "30 code" associated with a 1981 Cadillac Sedan DeVille. Vehicle identification numbers (VINs) and trim codes are used to identify specific features and options. A "30 code" isn't part of Cadillac's typical identification system from that year.
To find information about a specific 1981 Cadillac Sedan DeVille, you'll need either the VIN or the trim tag (located usually on the driver's side doorjamb). These will provide the necessary details about the car's original specifications.
