GMPartsGiant.com offers the wholesale prices for genuine 2015 Cadillac ATS Coupe parts. Parts like Communication System 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, 4 Cyl 2.5L, 6 Cyl 3.6L. Model Code: 2 DOOR COUPE, 2 DOOR LUXURY COUPE, 2 DOOR PERFORMANCE COUPE, 3 DOOR PREMIUM COUPE.