GM RPO codes: where to find them and how the catalog reads them

What GM RPO codes are

General Motors has used Regular Production Option codes since at least the 1950s and fully standardized them in 1969. Each code is three letters and digits long and stands for one option or component, from an engine to a suspension package.

Some codes grew famous enough to become model names. Z28 and Z06 started life as option codes, and Z71 still marks the off-road suspension package on GM trucks. 9C1 is the Chevrolet police package, and L78 was one of Chevrolet’s big-block V8 engines.

G80 is a code you meet on a lot of work orders. It is the automatic locking rear axle that Chevrolet has offered on its pickups for more than 40 years, and it decides which differential parts the truck takes.

The Service Parts Identification label

Older GM vehicles carry a printed Service Parts Identification label, often shortened to SPID. It lists the VIN and a block of three-character RPO codes, and GM places it in the glove box or in the trunk.

Paper labels fade and go missing over the years. If yours is gone, the codes still exist in GM’s build record for that VIN. GM had moved its vehicle records into an electronic database by 1990, which is why a catalog can recover the codes for cars built decades ago.

The three-character RPO is the standard format, and the one you will meet on nearly every GM vehicle from the last fifty years. Older GM paperwork also used two-digit sales codes and group accessory codes, so a short code on a classic may belong to one of those systems instead.

From the 2018 model year: the QR code on the door pillar

Starting with the 2018 model year, GM added a QR code to the Certification label on every Buick, Cadillac, Chevrolet and GMC model. The label sits on the driver-side B pillar, except on the Corvette, where it is on the driver’s door.

Any free QR reader on a phone can scan it. According to GM TechLink, the result lists the VIN, model year, model, build month and year, the vehicle order number, up to 48 RPO codes sorted alphanumerically and the paint code. On newer vehicles this replaces the printed list in the glove box.

The paint code in the same scan saves a second search when you order a painted panel or a touch-up. Our post on finding the paint code by VIN covers the other brands.

How the GM catalog uses RPO codes

The GM parts catalog decodes a VIN to the factory build and shows the RPO information that goes with it. Its parts lists can then be filtered to that build, so a Silverado with the G80 locker narrows to the axle parts that match its build.

The catalog also has an RPO search. Enter a code you read off a label and it tells you what the option is, which is quicker than an internet list that may not match your model year. Our guide to American cars by VIN covers the rest of the Detroit catalogs.

When the code decides the part

RPO codes earn their keep where one model takes two versions of a part. Brake packages, axle ratios, trailering equipment, suspension packages and engines all split this way, and the VIN alone does not always spell out the split.

Read the codes before you order, then check them against the catalog’s filtered result. If a code on the label disagrees with the VIN decode, trust the car in front of you and look at the part itself, since previous owners swap axles and engines.

Chevrolet, GMC, Cadillac and Buick on VINsearch

VINsearch opens the GM catalog for Chevrolet, GMC, Cadillac and Buick in one login. Enter the VIN and the catalog applies the factory build for you, including its RPO codes. Start at the Chevrolet catalog, or read the manufacturer, country and year first with the free VIN decoder.