Vehicle identification number

The first three characters uniquely identify the manufacturer of the vehicle using the world manufacturer identifier or WMI code. A manufacturer who builds fewer than 1,000 vehicles per year uses a 9 as the third digit, and the 12th, 13th and 14th position of the VIN for a second part of the identification. Some manufacturers use the third character as a code for a vehicle category (e.g., bus or truck), a division within a manufacturer, or both. For example, within 1G (assigned to General Motors in the United States), 1G1 represents Chevrolet passenger cars; 1G2, Pontiac passenger cars; and 1GC, Chevrolet trucks.

The Society of Automotive Engineers (SAE) in the US assigns WMIs to countries and manufacturers.[8]

The first character of the WMI is the region in which the manufacturer is located. In practice, each is assigned to a country of manufacture, although in Europe the country where the continental headquarters is located can assign the WMI to all vehicles produced in that region (Example: Opel/Vauxhall cars whether produced in Germany, Spain, the United Kingdom or Poland carry a WMI of W0L because Adam Opel AG is based in Rüsselsheim, Germany).

In the notation below, assume that letters precede numbers and that zero is the last number. For example, 8X–82 denotes the range 8X, 8Y, 8Z, 81, 82, excluding 80.[8]

The fourth to ninth positions in the VIN are the vehicle descriptor section or VDS. This is used, according to local regulations, to identify the vehicle type, and may include information on the automobile platform used, the model, and the body style. Each manufacturer has a unique system for using this field. Most manufacturers since the 1980s have used the eighth digit to identify the engine type whenever there is more than one engine choice for the vehicle. Example: for the 2007 Chevrolet Corvette, U is for a 6.0-liter V8 engine, and E is for a 7.0-liter V8.

One element that is inconsistent is the use of position nine as a check digit, compulsory for vehicles in North America and China, but not Europe.

The 10th to 17th positions are used as the vehicle identifier section or VIS. This is used by the manufacturer to identify the individual vehicle in question. This may include information on options installed or engine and transmission choices, but often is a simple sequential number. In North America, the last five digits must be numeric.

One consistent element of the VIS is the 10th digit, which is required worldwide to encode the model year of the vehicle. Besides the three letters that are not allowed in the VIN itself (I, O and Q), the letters U and Z and the digit 0 are not used for the model year code. The year code is the model year for the vehicle.

The year 1980 was encoded by some manufacturers, especially General Motors and Chrysler, as "A" (since the 17-digit VIN was not mandatory until 1981, and the "A" or zero was in the manufacturer's pre-1981 placement in the VIN), yet Ford and AMC still used a zero for 1980. Subsequent years increment through the allowed letters, so that "Y" represents the year 2000. 2001 to 2009 are encoded as the digits 1 to 9, and subsequent years are encoded as "A", "B", "C", etc.

On April 30, 2008, the US National Highway Traffic Safety Administration adopted a final rule amending 49 CFR Part 565, "so that the current 17 character vehicle identification number (VIN) system, which has been in place for almost 30 years, can continue in use for at least another 30 years", in the process making several changes to the VIN requirements applicable to all motor vehicles manufactured for sale in the United States. There are three notable changes to the VIN structure that affect VIN deciphering systems:

• The make may only be identified after looking at positions one through three and another position, as determined by the manufacturer in the second section or fourth to eighth segment of the VIN.
• In order to identify the exact year in passenger cars and multipurpose passenger vehicles with a GVWR of 10,000 or less, one must read position 7 as well as position 10. For passenger cars, and for multipurpose passenger vehicles and trucks with a gross vehicle weight rating of 10,000 lb (4,500 kg) or less, if position seven is numeric, the model year in position 10 of the VIN refers to a year in the range 1980–2009. If position seven is alphabetic, the model year in position 10 of VIN refers to a year in the range 2010–2039.
• The model year for vehicles with a GVWR greater than 10,000 lb (4,500 kg), as well as buses, motorcycles, trailers and low-speed vehicles, may no longer be identified within a 30-year range. VIN characters 1–8 and 10 that were assigned from 1980–2009 can be repeated beginning with the 2010 model year.

Compulsory in North America and China is the use of the 11th character to identify the assembly plant at which the vehicle was built. Each manufacturer has its own set of plant codes.

In the United States and China, the 12th to 17th digits are the vehicle's serial or production number. This is unique to each vehicle, and every manufacturer uses its own sequence.

Transliteration consists of removing all of the letters, and replacing them with their appropriate numerical counterparts. These numerical alternatives (based on IBM's EBCDIC) are in the following chart. I, O, and Q are not allowed in a valid VIN; for this chart, they have been filled in with N/A (not applicable). Numerical digits use their own values.

S is 2, and not 1. There is no left-alignment linearity.

The following is the weight factor for each position in the VIN. The 9th position is that of the check digit. It has been substituted with a 0, which will cancel it out in the multiplication step.

Consider the hypothetical VIN 1M8GDM9A_KP042788, where the underscore will be the check digit.

1. The VIN's value is calculated from the above transliteration table. This number is used in the rest of the calculation.
2. Copy the weights from the above weight factor table.
3. The products row is the result of the multiplication of the vertical columns: Value and Weight.
4. The products (8, 28, 48, 35 ... 24, 16) are all added together to yield a sum, 351.
5. Find the remainder after dividing by 11
   351 MOD 11 = 10
   351 ÷ 11 = 31 ¹⁰/₁₁
6. The remainder is the check digit. If the remainder is 10, the check digit is X. In this example, the remainder is 10, so the check digit is transliterated as X.

With a check digit of X, the VIN 1M8GDM9A_KP042788 is written 1M8GDM9AXKP042788.

A VIN with straight-ones (seventeen consecutive 1s) has the nice feature that its check digit 1 matches the calculated value 1. This is because a value of one multiplied by 89 (sum of weights) is 89, and 89 divided by 11 is 8 with remainder ​¹⁄₁₁; thus 1 is the check digit. This is a way to test a VIN-check algorithm.