Start with positions 1–3
The first three characters of a standard VIN form its WMI. The code belongs to a controlled manufacturer-identification system. Looking up the complete WMI is more useful than interpreting one character in isolation because the assignment concerns a manufacturer and may also distinguish vehicle types.
In the sample VIN 1G4AH59H45G118341, the three-character WMI is 1G4. The remaining characters are needed to decode the particular vehicle. A WMI lookup alone does not establish its model, model year, engine, or trim.
Assignment region is different from assembly location
WMI assignments are organized geographically, but that geography should not be treated as proof of a particular vehicle’s final assembly country. The assignment describes the manufacturer-identification system; the actual plant must be supported by the manufacturer’s VIN records or other vehicle documentation.
Some manufacturers use an extended identifier
For low-volume manufacturers using the U.S. six-character identifier structure, position 3 is 9. Positions 1–3 are combined with positions 12–14 to identify the manufacturer and vehicle type. Reading only the initial three characters can therefore leave the manufacturer unresolved.
As a structural illustration, a prefix AB9 together with XYZ in positions 12–14 forms the lookup key AB9XYZ. These letters are a made-up demonstration of the extraction method, not a claim that this WMI is assigned to a real manufacturer.
NHTSA’s DecodeWMI endpoint accepts either a three-character code or the six characters from positions 1–3 and 12–14. When detailed decoding does not identify a manufacturer, this site can use the appropriate WMI lookup as a separate source of limited information.
If the lookup returns no manufacturer
A missing WMI result may reflect database coverage, an assignment that is not represented in the source, a transcription error, or an unavailable service. It does not justify inventing a manufacturer from a similar-looking code. Keep the original VIN and ask the vehicle manufacturer or registration authority to confirm it.
The useful distinction is between the literal WMI characters, which can always be extracted from an accepted input, and a verified manufacturer assignment, which requires supporting data.