GMPartsGiant.com offers the wholesale prices for genuine 2017 Cadillac CTS Sedan parts. Parts like Sunroof are shipped directly from authorized GM dealers and backed by the manufacturer's warranty. Parts fit for the following vehicle options. Engine: 4 Cyl 2.0L, 6 Cyl 3.6L. Model Code: 4 DOOR PERFORMANCE SEDAN, 4 DOOR PLUS SEDAN, 4 DOOR PREMIUM SEDAN.