The General Motors Sigma platform is a mid-size automobile platform used by General Motors from the 2003 to 2015 model years. Exclusive to the

Cadillac The Cadillac Motor Car Division () is a division of the American automobile manufacturer General Motors (GM) that designs and builds luxury vehicles. Its major markets are the United States, Canada, and China. Cadillac models are distributed ...

division, Sigma was the successor to the Opel-designed V platform. Initially developed for

executive cars Executive car is a British term for a large car which is equivalent to the European E-segment and American full-size classifications. Executive cars are larger than compact executive cars (and the non-luxury equivalent mid-size cars), and smal ...

, the architecture was expanded for larger model lines, sports sedans, and multiple body styles. Two generations of the Sigma platform were developed by GM for worldwide markets. The architecture was discontinued for the 2016 in favor of the

GM Alpha platform The GM Alpha platform currently underpins General Motors' compact to mid-size, front-engine, rear-wheel and four-wheel drive vehicles. Platform basics include MacPherson struts on the front, 5 link independent rear, use of high strength steel ...

, itself utilized nearly exclusive by Cadillac.

Sigma I

The first Cadillac-exclusive platform since the D-body chassis, Sigma debuted in early 2002 for the 2003 model year underpinning the

Cadillac CTS The Cadillac CTS is an executive car that was manufactured and marketed by General Motors from 2003 until 2019 across three generations. Historically, it was priced similarly to cars on the compact luxury spectrum; but it has always been sized ...

, replacing the Cadillac Catera. Slightly larger than its V-body predecessor, the rear-wheel drive Sigma architecture was developed to accommodate all-wheel drive and extended-wheelbase variants. For 2004, the

Cadillac STS The Cadillac STS (Seville Touring Sedan) is a mid-sized luxury 4-door sedan manufactured and marketed by General Motors from 2004 to 2011 for the 2005 to 2011 model years. A version of the STS was sold in China as the SLS through 2013. It wa ...

was introduced on the Sigma platform, replacing the Cadillac Seville. Sharing its wheelbase with the STS, the

Cadillac SRX The Cadillac SRX is a mid-size luxury SUV and compact luxury crossover SUV (CUV) manufactured and marketed by Cadillac over two generations: the first generation as a five-door, three-row, seven-passenger CUV (2003–2009), and the second genera ...

was introduced for 2005 as the second Cadillac SUV, slotted below the Escalade in size. The Sigma platform uses four-wheel independent suspension with front control arms and a rear multi-link configuration. Initially powered by variants of the

General Motors 54° V6 engine General Motors' Opel subsidiary in Europe designed a compact V6 engine with an unusual 54° vee angle. It was an iron block/aluminum head DOHC design with 4 valves per cylinder. All 54° engines were assembled at Ellesmere Port in England. Histo ...

family, the platform introduced additional engines, including the High Feature V6 and Northstar V8. Exclusive to the high-performance CTS-V, the Sigma platform was developed to accommodate the 5.7L LS6 and 6.0L LS2 V8 engines of the Chevrolet Corvette. Outside of the CTS (which offered a standard 5-speed manual and a 6-speed manual for the CTS-V), all Sigma vehicles utilized GM 5-speed 5L40/5L50 automatic transmissions. The Sigma architecture marked several firsts, as the CTS was the first Cadillac since the 1986 Cadillac Cimarron to be offered with a manual transmission. The 2004 STS became the first rear-wheel drive Cadillac sedan to offer the Northstar engine (originally developed for front-wheel drive applications). The China-market Cadillac SLS became the first non-limousine Cadillac sedan line introduced as a extended-wheelbase variant. Vehicles based on this platform: * 2003–2007

* 2004–2009

* 2005–2011

* 2007–2013 Cadillac SLS (China)

Sigma II

GM debuted Sigma II with the 2008 Cadillac CTS. While sharing the previous 113.4-inch wheelbase, the platform was longer and wider than the previous generation. Remaining exclusive to the Cadillac division, the design adopted a greater degree of parts sharing with the Australian-designed Zeta platform. The High Feature engines were carried over to Sigma II, with the CTS-V receiving a supercharged LSA V8 (a variant of the Corvette ZR1 engine). Sigma II became exclusive to the CTS, as the SRX was downsized for 2010, adopting the Theta Premium architecture and the STS was retired after 2011 (the SLS, 2013) with no direct successor. For 2011,

coupé A coupe or coupé (, ) is a passenger car with a sloping or truncated rear roofline and two doors. The term ''coupé'' was first applied to horse-drawn carriages for two passengers without rear-facing seats. It comes from the French past parti ...

and

station wagon A station wagon ( US, also wagon) or estate car ( UK, also estate), is an automotive body-style variant of a sedan/saloon with its roof extended rearward over a shared passenger/cargo volume with access at the back via a third or fifth door ( ...

variants were introduced on the Sigma II platform (marking the first Cadillac coupe with a rear seat since the 2002 Eldorado) Applications: * 2008–2013

* 2009–2015

Cadillac CTS-V The Cadillac CTS is an executive car that was manufactured and marketed by General Motors from 2003 until 2019 across three generations. Historically, it was priced similarly to cars on the compact luxury spectrum; but it has always been siz ...

References

{{General Motors platforms

Sigma Sigma (; uppercase Σ, lowercase σ, lowercase in word-final position ς; grc-gre, σίγμα) is the eighteenth letter of the Greek alphabet. In the system of Greek numerals, it has a value of 200. In general mathematics, uppercase Σ is used a ...