How to Decode GM VIN Codes

Locate the VIN number, which can be found on the plate attached to the left side of the instrument panel and is visible by looking through the windshield from the outside. The VIN can also be found on the Certification Label attached to the left door pillar or on the Vehicle Certificate of Title and Registration.

Identify the first three digits of the VIN. These represent the World Manufacturer Identification number. For GM vehicles, which are assigned the 1G initial designation, the following codes represent the manufacturing divisions of GM: 1G1 represents Chevrolet passenger cars; 1G2, Pontiac passenger cars; and 1GC, Chevrolet trucks.

Find the next five digits. This is the Vehicle Description Section of the VIN code. For GM vehicles, the fourth and fifth digits represent the platform and series. The sixth digit is the body type. For GM vehicles, 1 is a two-door coupe; 2 is a two-door; 3 is a two-door convertible; 5 is a four-door sedan; 6 is a four-door hatchback; 8 is a four-door wagon/two-door hatchback; 9 is a four-door station wagon. The seventh digit designates the restraint system and the eighth digit defines the engine type.

The next three digits represent production numbers. The ninth digit is known as the check digit, which is used for VIN validation based upon a calculation developed by the Department of Transportation. The tenth digit is a letter that represents a vehicle model year. For GM, "X" stands for the 1999 model year, "Y" is for 2000, "1" is for 2001, "2" is for 2002 and so on. The eleventh digit represents the assembly plant where the vehicle was manufactured.

The remaining six digits are the vehicle's serial number, which are assigned sequentially based upon production order with the first vehicle being 100001.