The Cadillac CTS has been available since its introduction as a 2003 model. To decide whether your CTS has a 3.2-liter or 3.5-liter engine, you can decode the vehicle identification number (VIN), which not only identifies cars as an anti-theft measure but also tells you about general features of the car, such as engine type, factory of origin, and whether it accepts ethanol gas.
Locate the VIN in the lower-right corner of the windshield, stamped or etched on a plate attached to the dashboard.
Ensure that the third character is a 6 to confirm it's a Cadillac.
Check that the fourth and fifth characters are DM, DN, DP, or DR to confirm that it's a CTS. These are for 2006 model. These two characters vary by year model. For example, the set for a 2003 model is DG, DM, DR, or DU.
Check the eighth character. J means the engine is a 3.1-liter V6. M and 8 both mean it's a 3.5-liter V6. 7 means it's a 3.6-liter V6. There is no GM 3.2-liter engine of any number of cylinders among 2006 models. For 2003 models, N indicates a 3.2-liter V6. There are no 3.6-liter engines for model year 2003.
