ISO 3779 & US 49 CFR Part 565 VIN Validator Engine

Zero-dependency TypeScript library for validating 17-character Vehicle Identification Numbers (VINs), verifying mathematical Position 9 Modulo-11 check digits, and decoding 30-year cyclic model years under ISO 3779 and US 49 CFR Part 565.

Live interactive implementation: UseCOS VIN Decoder & Recall Hub.

Overview

Under ISO 3779, ISO 3780, and the United States National Highway Traffic Safety Administration (NHTSA 49 CFR Part 565), every road vehicle manufactured since 1981 carries a unique 17-character Vehicle Identification Number.

In North America, position 9 is reserved as a mandatory mathematical check digit calculated via a weighted modulo 11 algorithm. This check detects over 95% of transcription errors, accidental typos, and fraudulent VIN tampering.

VIN Structure Anatomy

A 17-character VIN is broken into three distinct international sections:

| Characters | Section | Name | Description | | :--- | :--- | :--- | :--- | | 1 – 3 | WMI | World Manufacturer Identifier | Geographic region, country of manufacture, and vehicle manufacturer. | | 4 – 8 | VDS | Vehicle Descriptor Section | Model line, body style, engine type, transmission, and restraint systems. | | 9 | Check | Check Digit | Mathematical verification digit (0–9 or X). | | 10 | VIS | Model Year | 30-year cyclic alphanumeric encoding representing the vehicle year. | | 11 | VIS | Assembly Plant | Manufacturer-specific assembly plant identification code. | | 12 – 17 | VIS | Sequential Production Number | Unique vehicle serial number on the production line. |

Prohibited Characters: Under ISO 3779 § 4.1, the letters I, O, and Q are strictly forbidden to prevent visual confusion with the digits 1 and 0.

Check Digit Algorithm & Mathematical Formulation

1. Transliteration Values

Each alphanumeric character is mapped to a designated integer value:

| Character | Value | Character | Value | Character | Value | | :--- | :--- | :--- | :--- | :--- | :--- | | 0 – 9 | $0 - 9$ | E | $5$ | P | $7$ | | A, J | $1$ | F | $6$ | R | $9$ | | B, K, S | $2$ | G | $7$ | T | $3$ | | C, L, T | $3$ | H | $8$ | U | $4$ | | D, M | $4$ | N | $5$ | V | $5$ | | W | $6$ | X | $7$ | Y | $8$ | | Z | $9$ | | | | |

2. Positional Weight Vector

Each position in the 17-character string is assigned a statutory weight:

$$\vec{w} = [8, 7, 6, 5, 4, 3, 2, 10, 0, 9, 8, 7, 6, 5, 4, 3, 2]$$

(Notice weight $0$ at index 8 corresponds to position 9, the check digit itself).

3. Modulo 11 Calculation

$$\text{Sum} = \sum_{i=1}^{17} \vec{w}_i \cdot v(c_i)$$

$$\text{Check Digit} = \text{Sum} \pmod{11}$$

If $\text{Remainder} = 10$, the check character is represented by Roman numeral X.

Model Year Cyclic Decoding (Position 10)

Model years rotate through a 30-year cycle using 21 uppercase letters (omitting I, O, Q, U, Z) followed by digits 1–9:

• Cycle 1 (1980–2000): A (1980) $\dots$ Y (2000)
• Cycle 2 (2001–2009): 1 (2001) $\dots$ 9 (2009)
• Cycle 3 (2010–2030): A (2010) $\dots$ Y (2030)

Installation & Usage

npm install iso-3779-vin-validator

TypeScript Example:

import { validateVin, decodeModelYear } from 'iso-3779-vin-validator';

// 1. Validate a complete 17-character VIN
const result = validateVin('1HGCM82633A004352');

if (result.valid) {
  console.log('WMI:', result.wmi);                       // "1HG" (Honda USA)
  console.log('Check Digit:', result.checkDigit);       // "3"
  console.log('Model Year:', result.modelYear);         // 2003
  console.log('Serial Number:', result.sequentialNumber); // "004352"
} else {
  console.error('Validation failed:', result.error);
}

// 2. Decode model year directly
console.log(decodeModelYear('P')); // 2023
console.log(decodeModelYear('T')); // 2026

Edge Cases: North America vs European Market (EU)

While all modern vehicles sold in the United States, Canada, and Mexico mandate the mathematical check digit at position 9 under federal regulation, European domestic vehicles (which do not export to North America) sometimes treat position 9 as an arbitrary manufacturer-assigned descriptor code.

This engine flags non-matching check digits while clearly identifying whether the syntax adheres to ISO 3779 structure.

Live Implementation & Tools

• Interactive Vehicle Lookup: UseCOS Free VIN Decoder & Recall Hub
• Used Car Cross-Check: UseCOS Used Car VIN Mismatch & Scam Checker
• Ontario UVIP Checklist: UseCOS Used Vehicle Information Package Guide

License

MIT © UseCOS Engineering. Open-source for developers, automotive engineers, and consumer protection platforms.