GM VIN Decoder Guide: decode Chevrolet, GMC, Cadillac & Buick VINs (properly)
A GM VIN is a 17‑character “configuration fingerprint.” It can tell you where the vehicle was built, what GM brand/type it is, model year, plant, and (for many lines) engine family and trim/series. The trick: GM doesn’t encode every line the same way — trucks, MPVs and passenger cars use different logic.
Choose the right GM brand VIN decoder
GM is a group — but VIN decoding is most accurate when you use a brand‑aware decoder. Pick your badge below (each button opens a 7zap VIN decoder in a new tab).
Decode a Chevrolet VIN to identify line/trim (e.g., Silverado LTZ vs RST), engine family (e.g., L84, L3B, L87, LZ0), plant, year, and parts catalogs.
GMC VIN decoding is especially useful for confirming chassis/series combinations (2WD vs 4WD, Denali Ultimate vs AT4X, HD vs 1500) before buying parts or a used truck.
Cadillac VINs often make it easy to confirm plant and engine family, while series codes reveal luxury trims (Luxury, Premium Luxury, Sport, etc.).
Buick VIN decoding is where “global GM” shows up fast: the WMI can indicate Korea or China, and the plant code makes a big difference for parts catalogs and trim identification.
Why we don’t offer a universal “GM VIN checker” button: GM uses multiple WMIs and encoding tables across brands and regions. If you decode a GMC VIN with a Chevrolet tool (or vice‑versa), you can get partial or misleading results.
Start with the first 3 VIN characters. They usually tell you which GM brand/type table to use. Here’s a visual cheat-sheet for the most common groups you’ll see on modern GM vehicles.
What GM VIN decoding can (and can’t) tell you
A VIN is not a full build sheet — but it’s far more than a serial number. Here’s what you can reliably extract for most GM vehicles, plus where you may need GM option (RPO) data.
- Brand/type and manufacturer context (WMI, positions 1–3)
- Model year (position 10)
- Assembly plant code (position 11 — decode in correct context)
- Engine family via VIN engine code (position 8, model‑specific mapping)
- Truck chassis/series (2WD/4WD + trim in positions 5–6 for many GM trucks)
- Packages with overlapping names (towing/max towing variants, off‑road packages)
- Axle ratio & differential type (often tracked via RPO codes)
- Interior tech bundles, wheel packages, audio systems
- Country‑specific equipment differences for export models
Practical rule: Use the VIN to lock in the correct vehicle line/engine/plant, then confirm the remaining equipment via GM build/option codes (RPO) or the brand decoder’s details.
GM VIN structure: the 17 positions (with GM-specific meaning)
Every modern GM VIN follows the 17‑character format. But GM uses different “semantics” for passenger cars vs trucks/MPVs — especially around positions 4–6. Click a position below to see what it usually represents.
Start with positions 1–3 (WMI)
On GM vehicles, the first three characters are the World Manufacturer Identifier. They tell you the build region, manufacturer entity, and (often) the GM brand/type — which is the key to choosing the correct decoder.
GM quick map
- 1–3 (WMI): build region + GM entity + brand/type
- 4–8 (VDS): vehicle line / chassis / series / body + engine (varies by line)
- 9: check digit (validates VIN)
- 10: model year code
- 11: assembly plant code (decode with context)
- 12–17: sequential production number
GM-specific gotcha
- Passenger cars: position 4 is often vehicle line, position 5 series, position 6 body style.
- Trucks/MPVs: position 4 often carries GVWR/brake/body style, position 5 chassis, position 6 series.
- Plant codes can repeat across GM lines — don’t decode “F” or “Z” in isolation.
Don’t overfit a single table: GM VIN tables can be vehicle‑line specific. The right decode depends on the brand/type (WMI), year, and product line.
WMI (positions 1–3): the fastest way to identify the GM brand & region
The WMI is your “routing code.” It points you to the correct brand decoder and the correct decoding table. Here are GM‑specific examples you’ll see in the real world (North America + global GM).
North America (common GM WMIs)
These usually start with 1 (USA), 2 (Canada) or 3 (Mexico).
1G1— Chevrolet passenger car (example: Malibu)1GC— Chevrolet truck (example: Silverado/Express)1GT— GMC truck (example: Sierra/Savana)1G6— Cadillac passenger car (example: CT4)1GY— Cadillac MPV/SUV (example: XT5, Escalade IQ)3GN— Chevrolet MPV built in Mexico (example: Equinox)
Global GM (you’ll see these on modern crossovers)
GM builds vehicles globally — so GM VINs can start with letters (like K or L).
KL4— Buick MPV built in South Korea (example: Encore GX)KL7— Chevrolet MPV built in South Korea (example: Trailblazer/Trax)LRB— Buick MPV built in China (SAIC‑GM) (example: Envision)
Shortcut: if the first three characters look like 1G…,
you’re usually dealing with a North‑American GM VIN table. If it’s KL… or LR…,
you’re in “global GM,” and region‑specific decoding becomes more important.
| WMI example | Typical meaning | What to do next |
|---|---|---|
1G1 |
Chevrolet passenger car (USA context) | Use the Chevrolet decoder and treat positions 4–6 as line/series/body style. |
1GC |
Chevrolet truck (often Silverado/Express lines) | Decode chassis/series (positions 5–6) as drivetrain + trim; confirm engine code (8th). |
1GT |
GMC truck | Use the GMC decoder; check 2WD/4WD + trim mapping in 5–6. |
KL4 |
Buick MPV (GM Korea) | Use the Buick decoder; plant and series codes will follow Korea mapping. |
LRB |
Buick MPV (SAIC‑GM, China) | Decode with Buick tools; plant codes and engine codes can differ from US/Canada models. |
VDS (positions 4–8): where GM encodes chassis, series, and core configuration
This is the part of the VIN where GM gets “brand‑and‑line specific.” If you want the most accurate decode, use a brand‑aware decoder — but understanding the logic helps you verify listings and parts.
For many GM passenger cars, positions 4–5 identify the vehicle line + series, and position 6 is the body type. In other words: the VIN itself often tells you “what line it is” (Malibu vs something else) and which series/trim family it belongs to.
For many GM trucks and MPVs, position 4 is tied to GVWR / brake system / body style, position 5 identifies the chassis/drivetrain (commonly 2WD vs 4WD), and position 6 maps to series/trim.
GM truck decoding tip: For Silverado/Sierra 1500, you’ll often see a two‑character chassis/series code that can be read as “drivetrain + trim.” Example patterns are shown below in the case studies section.
VDS Why do positions 4–6 feel different between a Malibu and a Silverado?
VDS Can the VDS tell me “RST vs LTZ” or “Denali vs AT4X”?
Check digit (9th character): a built-in VIN “typo detector”
The 9th character is a calculated check digit. Think of it as a checksum:
it helps catch mistyped VINs and can flag suspicious or invalid numbers.
On many GM VINs, the check digit can be a number 0–9 or X (where X represents the value 10).
- Copy/paste errors (a single wrong character often breaks the check digit)
- Confusing letters and numbers (e.g.,
Ovs0,Svs5) - Screen-captured VINs or listings with formatting issues
- Basic fraud screening (a “random” VIN often fails the checksum)
- It does not prove the vehicle is legitimate or unmodified.
- It does not validate the title, history, mileage, or theft status.
- A cloned VIN can still have a valid check digit.
How it’s calculated (high level): each VIN character is converted into a numeric value,
multiplied by a position weight, summed, then reduced by a modulo operation (mod 11).
If the remainder is 10, the check digit becomes X.
Math I want the full algorithm. What are the weights?
A common VIN check-digit system uses these position weights (1→17):
8, 7, 6, 5, 4, 3, 2, 10, 0, 9, 8, 7, 6, 5, 4, 3, 2.
Position 9 has weight 0 because it is the check digit itself.
Math How are letters converted to numbers?
VIN transliteration maps letters to numbers (I, O and Q are not used in VINs). Example mapping groups: A/J=1, B/K/S=2, C/L/T=3, D/M/U=4, E/N/V=5, F/W=6, G/P/X=7, H/Y=8, R/Z=9. Numbers keep their numeric value.
Practical tip: if a VIN fails the check digit, the fastest fix is usually correcting one character. If you’re decoding a GM VIN for parts, use a brand decoder — it will also catch obvious formatting mistakes.
Model year code (10th character): the universal VIN year table
The 10th VIN character encodes the model year. The catch: the code repeats every 30 years, so you must use context (vehicle generation, paperwork, or decoder output) to distinguish 1985 vs 2015, etc.
Year codes repeat. Always sanity-check the year against the vehicle’s generation and features.
| Code | Years (cycles) | Code | Years (cycles) |
|---|---|---|---|
A | 1980, 2010, 2040 | L | 1990, 2020, 2050 |
B | 1981, 2011, 2041 | M | 1991, 2021, 2051 |
C | 1982, 2012, 2042 | N | 1992, 2022, 2052 |
D | 1983, 2013, 2043 | P | 1993, 2023, 2053 |
E | 1984, 2014, 2044 | R | 1994, 2024, 2054 |
F | 1985, 2015, 2045 | S | 1995, 2025, 2055 |
G | 1986, 2016, 2046 | T | 1996, 2026, 2056 |
H | 1987, 2017, 2047 | V | 1997, 2027, 2057 |
J | 1988, 2018, 2048 | W | 1998, 2028, 2058 |
K | 1989, 2019, 2049 | X | 1999, 2029, 2059 |
Y | 2000, 2030, 2060 | 1 | 2001, 2031, 2061 |
2 | 2002, 2032, 2062 | 6 | 2006, 2036, 2066 |
3 | 2003, 2033, 2063 | 7 | 2007, 2037, 2067 |
4 | 2004, 2034, 2064 | 8 | 2008, 2038, 2068 |
5 | 2005, 2035, 2065 | 9 | 2009, 2039, 2069 |
If your 10th character is S, that could be 1995 or 2025.
A brand decoder (Chevrolet/GMC/Cadillac/Buick) resolves the ambiguity instantly using WMI + generation context.
Plant code (11th character): why you shouldn’t decode it “by the letter”
The 11th character is the assembly plant code. The important GM nuance: plant codes can overlap across vehicle lines — so you must decode the plant using the right GM table (brand + line + year).
GM reality check: the same plant code character can mean different plants in different GM lines.
| Vehicle line example | Plant code (11th) | Plant (in that specific GM context) | Why it matters |
|---|---|---|---|
| Chevrolet Malibu (passenger car) | F |
Fairfax (USA context) | Confirms the manufacturing site for that car line; useful for supply chain/parts variations. |
| Chevrolet Silverado HD / GMC Sierra HD | F |
Flint (USA context) | Same letter, different plant — a great example of why “plant-code lists” can mislead. |
| Chevrolet Silverado / GMC Sierra 1500 | Z / 1 / G |
Fort Wayne (USA) / Oshawa (Canada) / Silao (Mexico) | Plant can indicate country-specific part catalogs and build differences. |
| Chevrolet Equinox (Mexico build) | S |
Ramos Arizpe (Mexico context) | Export/import vehicles often require stricter parts confirmation — plant helps. |
| Buick Encore GX (South Korea build) | B |
Bupyeong (Korea context) | Global WMIs change the entire decode table; plant confirms the region-specific catalog. |
| Buick Envision (China build) | D |
Dong Yue (China context) | Same brand, different region — major difference for parts and trim packages. |
| Cadillac XT5 / XT6 (USA context) | Z |
Spring Hill (USA context) | Useful when verifying listings or cross-checking “made in” claims. |
| Cadillac CT4 (USA context) | 0 |
Lansing – Grand River (USA context) | Shows numeric plant codes are common too, not only letters. |
| Cadillac Escalade IQ (EV MPV) | U |
Detroit Hamtramck (USA context) | EV lines follow GM MPV/truck logic; plant helps verify build origin. |
Bottom line: decode the plant after you’ve identified the GM brand/type and vehicle line. The right 7zap decoder does that automatically, with the correct context.
Engine code (8th character): GM’s “engine family shortcut”
For many GM lines, the 8th character maps to a specific engine family. It’s not always the full marketing engine name — but it’s accurate enough to prevent expensive mistakes in parts selection.
Example: Silverado / Sierra 1500 engine codes
These are common modern GM truck engine families mapped by the 8th VIN character.
| 8th character | Engine family (example) |
|---|---|
D | L84 — 5.3L V8 gasoline (common GM truck engine family) |
K | L3B — 2.7L turbo gasoline (truck) |
L | L87 — 6.2L V8 gasoline |
8 | LZ0 — 3.0L turbo diesel (Duramax family) |
Example: commercial vans (Express / Savana)
GM vans often show a clean engine mapping in the VIN, helpful for fleet service and ordering.
| 8th character | Engine family |
|---|---|
P | LV1 — 4.3L V6 gasoline |
1 | LWN — 2.8L diesel |
7 | L8T — 6.6L V8 gasoline |
Do not assume engine codes are universal across all GM vehicles. A character that means one engine on a truck line can mean something else on a passenger car line. Always decode engine code in the right GM context.
8th Is the engine code the same as the GM RPO engine code?
Options & RPO codes: the “second layer” of GM decoding
If the VIN is the skeleton, RPO codes are the organs. GM’s Regular Production Option (RPO) codes describe packages and equipment that a VIN may not fully detail.
Where this matters most: towing packages, axle ratios, differential type, suspension packages, infotainment systems, and market‑specific equipment.
- Decode VIN to lock in line + engine + year + plant.
- Confirm equipment using RPO/build data (or decoder output).
- Use RPO codes to resolve ambiguous packages (e.g., “tow package” can mean different things).
- VIN confirms the core platform and engine family.
- RPO/build data confirms the exact equipment set.
- For used vehicles: also check the physical stickers/labels and the vehicle itself.
RPO Why GM people talk about “RPO codes” so much?
RPO Are engine identifiers like L84 / L5P “RPO codes”?
Case studies: decoding real GM patterns (by brand)
Below are concrete GM examples showing how the same VIN positions “mean different things” across lines. Use this to sanity-check listings and to understand what a brand decoder is doing behind the scenes.
1) Chevrolet Malibu (passenger car logic)
Passenger cars often use positions 4–6 as vehicle line / series / body type. Example pattern: 1G1Z…
- WMI:
1G1= Chevrolet passenger car (USA context) - 4–5 (line/series): Book
Zwith series likeZB(LS),ZD(LT),ZE(Premier) - 8 (engine): example engine family
LFV(VIN codeTon some Malibu mappings) - 11 (plant): example plant code
F= Fairfax (in that line’s context)
2) Chevrolet Silverado 1500 (truck chassis/series logic)
Silverado uses positions 5–6 as a two-character “drivetrain + trim” key.
Example: AA vs KA.
| Pos 5–6 | Meaning (example mapping) |
|---|---|
AA | 4x2 / Work Truck (WT) |
AC | 4x2 / LT |
AD | 4x2 / RST |
KA | 4x4 / Work Truck (WT) |
KE | 4x4 / RST |
KJ | 4x4 / High Country |
Plant codes for 1500: in one modern mapping, Z=Fort Wayne (USA), 1=Oshawa (Canada), G=Silao (Mexico).
3) GMC Sierra 1500 (similar platform, different series codes)
Sierra also uses a 5–6 chassis/series key, but with GMC trims like SLE, Elevation, Denali, AT4X, Denali Ultimate.
| Pos 5–6 | Meaning (example mapping) |
|---|---|
HB | 2WD / SLE |
HC | 2WD / Elevation |
UE | 4WD / AT4 |
UF | 4WD / AT4X |
UG | 4WD / Denali |
UH | 4WD / Denali Ultimate |
4) Global GM: Buick (Korea/China) + Chevrolet (Mexico/Korea)
Same GM group, different WMIs and plants. This is why “GM VIN decoding” needs brand and region context.
- Buick Encore GX:
KL4(Korea), plant codeB(Bupyeong) - Buick Envision:
LRB(China SAIC‑GM), plant codeD(Dong Yue) - Chevrolet Equinox:
3GN(Mexico), plant codeS(Ramos Arizpe) - Chevrolet Trax/Trailblazer:
KL7(Korea), plant codesC(Changwon) orB(Bupyeong)
Takeaway: the first 3 characters do most of the routing work. Decode WMI first.
5) Cadillac: passenger car vs MPV/SUV vs EV
Cadillac uses WMIs like 1G6 (passenger car) and 1GY (MPV/SUV).
EV lines also follow MPV/truck-style mapping for many fields.
- CT4: WMI
1G6, plant code0(Lansing – Grand River), engine codesK/L/P - XT5: WMI
1GY, plant codeZ(Spring Hill), engine codesS(LGX) and4(LSY) - Escalade IQ: WMI
1GY, plant codeU(Detroit Hamtramck), engine type can reflect electric drive system
6) Commercial twist: Express & Savana include bus/incomplete WMIs
On some GM commercial lines, the WMI can indicate bus vs truck vs incomplete vehicle. In fleet and upfit scenarios, decoding the correct “type” matters.
- Express: valid WMIs can include
1GA,1GB,1GC, and more in certain contexts - Savana: valid WMIs can include
1GD,1GJ,1GT(plus special incomplete WMIs) - Plants: example plant
1= Wentzville; special incomplete variants can show different plant rules
Buying a used GM vehicle: a VIN-based checklist that actually works
If you’ve ever seen a listing like “Denali, maybe AT4? 6.2? not sure” — you already know why VIN decoding exists. Use this checklist to spot mismatches before you pay.
- WMI: confirm brand (Chevrolet vs GMC) and region.
- 5–6 chassis/series: confirm 2WD vs 4WD and trim family.
- 8 engine code: verify 2.7T vs 5.3 vs 6.2 vs diesel family.
- 10 year code: confirm model year matches listing.
- 11 plant: sanity-check build location (helps catch swapped VIN plates).
- WMI: confirm brand/type (Chevrolet passenger car vs Cadillac passenger car).
- 4–5 line/series: confirm series/trim family.
- 8 engine code: confirm engine family (turbo 4 vs performance V6, etc.).
- Plant code: cross-check plant for the line.
Red flag: when the VIN says one thing (engine, drivetrain, series), but the vehicle shows different badges or hardware. That can be an up-badge, a swapped powertrain, or a mismatched listing — and it’s exactly what a GM-aware VIN decode helps you catch.
Parts fitment workflow for GM: how to avoid ordering the wrong part
GM platforms share names across generations. “Silverado 1500” isn’t enough for parts. Use a VIN-based workflow to anchor to the correct catalog and the correct configuration.
- Identify the brand from WMI (Chevrolet vs GMC vs Cadillac vs Buick).
- Decode the VIN with the correct brand tool and open the parts catalog for your exact configuration: Chevrolet, GMC, Cadillac, Buick.
- Confirm engine family (VIN engine code, position 8) before ordering engine, cooling, exhaust or drivetrain parts.
- Confirm chassis/series on trucks (positions 5–6) for brake, suspension, body and axle components.
- If the part depends on packages (towing, off-road), verify with option/build data (RPO codes) where available.
Fast win: even if you don’t care about “VIN trivia,” decoding the VIN before ordering parts prevents the two most expensive errors: ordering the wrong engine family components and ordering the wrong drivetrain parts.
FAQ: GM VIN decoding
The questions people ask right before they accidentally buy the wrong part. (Or right after. We’re not judging.)
FAQ Is a GM VIN enough to know every option and package?
FAQ Why do different VIN websites give different answers for the same GM VIN?
FAQ Do GM plant codes repeat across different vehicles?
FAQ If my GM VIN starts with KL… or LR…, is it still a “GM VIN”?
FAQ What’s the safest way to decode a GM VIN online?
Chevrolet VIN decoder
GMC VIN decoder
Cadillac VIN decoder
Buick VIN decoder
Still unsure which brand decoder to use?
Start with the WMI (first 3 characters). If it looks like 1G1 → Chevrolet passenger,
1GC → Chevrolet truck, 1GT → GMC truck, 1G6 → Cadillac passenger,
1GY → Cadillac MPV, KL4 → Buick (Korea), LRB → Buick (China), KL7 → Chevrolet (Korea), 3GN → Chevrolet (Mexico).