GMPartsGiant.com offers the wholesale prices for genuine 2006 Cadillac STS parts. Parts like A/C Refrigeration System are shipped directly from authorized GM dealers and backed by the manufacturer's warranty. Parts fit for the following vehicle options. Engine: 6 Cyl 3.6L, 8 Cyl 4.4L, 8 Cyl 4.6L. Model Code: 4 DOOR, V 4 DOOR.