words: Wes Grueninger

The owner of the M3 felt his stomach twist into a walnut as the detective took a knife and began scraping paint off his car. After a few seconds, stamped numbers were visible, filled in with paint.. "Yep," the detective said. "This car's body is from a '91 that was stolen. The dash and the title are from an '89 that was wrecked. You can see where he swapped the VINs."

The what?

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There are 227 million cars and trucks on the road today, and the one thing they have in common is that they're all branded with a Vehicle Identification Number, or a VIN. While cars have been stamped with serial numbers for over a century, there was no firm standard for IDs until the National Highway Traffic Safety Administration laid down the 17-character VIN in 1981. Under the federal rules, each VIN is encoded with information about an individual car or truck. They identify a vehicle's automaker, model, production year, engine type, weight class, and place in the production run.

Each VIN is broken up into three sections, and in those sections each character has a specific meaning. When assigning those characters, every letter and numeral is used except for I, O, and Q, since they can be easily confused with 1 or 0.

The first section of a VIN is the World Manufacturer Identifier, a three-digit code assigned by the Society of Automotive Engineers based on what country a car is built in, the manufacturer, and-depending on the brand-either what division within the company actually builds the car, or the type of vehicle.

The first digit of the VIN determines the geographical region the car is built in, regardless of where the manufacturer is headquartered.

After the general area is nailed down, the next digit identifies the country in particular, and which manufacturer in that country.

For instance, the United States has some 33 second-digit codes that can be assigned to region codes 1, 4, and 5. Other countries, with fewer manufacturers, have to share region codes. France's fledgling auto industry is given only VINs from VF to VR, while Spain makes do with VS to VW. So a VIN that starts with 1G, 4G or 5G means "General Motors in the United States." The output of Toyota's North American plants is branded with 1T, 4T or 5T, while its Japanese plants produce cars with JT VINs.

The third digit represents, depending on which manufacturer, the division within the company or a specific body style. 1G1 is used to signify Chevrolet, while 1G2 is Pontiac, 1G4 is Buick, and so on. Ford, meanwhile, identifies each division in the second digit and the body type in the third. 1FA is a Ford passenger car, and 1FT covers Ford trucks, while 1LN is Lincoln passenger cars and 1L1 gets assigned to Lincoln commercial vehicles, such as limousines.

The second section of a VIN is known as the Vehicle Identifier Section. Made up of the fourth through ninth digits, this identifier contains the information that pins down exactly what kind of car the VIN is being assigned to, as well as a "check digit" that validates the VIN.

Each manufacturer codes the fourth through eighth digits of the VIN differently-with specific digits in a different order-but the information contained in it remains the same. The model of car, trim level, engine, and safety equipment are all contained in these four characters. Data gleaned from these digits are what allow insurance agents and banks to tell, at a glance, exactly what car they're dealing with.

The ninth digit is what's known as a "check digit," and it's used to validate a VIN. It makes it possible for a VIN to be self-checking. If a mistake is made in writing down the digits, or someone attempts to change out a few numbers to forge an ID, then the check digit will read incorrectly. Let's look at an example:

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The numeric characters are assigned a numeric value, and each position is multiplied by a succession of decreasing weighted numbers. The products are then added up to equal (insert total here), and divided by eleven to find the remainder. If the remainder is 10, it gets represented in the VIN as the Roman numeral "X."

The final section of every VIN is known as Vehicle ID Section, and comprises the VIN's tenth through seventeenth digits.

The tenth digit of a VIN is a year code. Whether or not it represents the year that the car was manufactured or the model year of the vehicle is up to the manufacturer, but the characters used to represent the year are codified in federal law. There are thirty characters-starting with "A" in 1980 and working their way up to "9" in 2009-that can be used in VINs, and since the same law that assigns the letters also mandates that no VINs can be reused for a period of thirty years, the date codes revert back to "A" in 2010.

The eleventh digit represents the car's assembly plant. Each manufacturer has its own codes, some represented by letters, and some by numbers, but either way, this code is required by law.

The final six digits are sequential and show a car's place in line during a production run. Usually starting with "100001" and counting up, the sequential number allows manufacturers to know exact cutoffs for when certain parts were used, making recalls easier to coordinate or service bulletins applicable to only a certain range of vehicles. The last six digits of the VIN can also be shuffled around depending on whether a manufacturer produces fewer than 500 cars per year. So-called "boutique" manufacturers populate the first three digits with "999," physically limiting the number of cars that can be built and assigned VINs.

Once a VIN has been coded, it's usually stamped on a steel plaque that is riveted to the driver's side of the dashboard. As restorers of classic cars have discovered, the plate itself is sacrosanct-it's illegal in many states to remove the plaque for any reason, including restoration-and if that plate is ever removed and lost, the car's VIN is recorded as scrapped, and the state issues a new vehicle ID number.

If dashboards can be swapped, and with them the VIN plaque, doesn't that make it easy for car thieves to whitewash a vehicle's provenance by purchasing a wrecked car and switching the identifying parts over to a stolen one? At first blush, it would seem that way, and for many small-time crooks, that's sufficient. But manufacturers also print the VIN on self-destructing tags that are placed on easily removable parts, and stamp the number at various places on the car's body and frame. To stay ahead of the chop shops, the locations of those stampings are moved around during a car's production. The VIN may even be stamped on the car's engine and transmissions. When a muscle car is being advertised as "numbers matching," that's what is meant-the serial number stamped on the drivetrain matches the car's VIN, meaning that the engine and transmission in the car now are the same ones that were installed at the factory.

A bigger problem than theft looms for VINs, however. As the vehicle population keeps increasing, manufacturers are running out of VINs. Similar to the problems that telephone companies faced with running out of area codes, the seemingly inexhaustible supply of VINs is rapidly drying up. And, just as with area codes, the solution is deceptively simple: SAE has found that by easing restrictions on the use of letters and digits, an exponential number of available VIN combinations can be created. Software that is made to work with existing VINs won't need to be rewritten, and millions of DMV forms won't need to be reprinted. NHTSA is on board with SAE's plan, and the agency has proposed making it effective as early as 2010. The 17-digit VIN, thought a few years ago to be nearing obsolescence, is going to stay with us for the foreseeable future.