Cars 2 was Pixar's first sequel not centered on Toy Story.
Released in 2011, Cars 2 followed Pixar's Toy Story sequels but was the studio's first feature sequel built around a different franchise. The film broadened the Cars setting into an international spy and racing adventure, with Lightning McQueen competing in the World Grand Prix and Mater drawn into espionage.
Before Cars 2, Pixar had made Toy Story 2 and Toy Story 3 as sequels to its original feature. Cars therefore became the next Pixar property to receive a feature-length continuation. Cars 3 later returned the series to Lightning's personal racing story and was the third Cars feature.
The wording matters because Cars 2 was not Pixar's first sequel overall. It was the first sequel outside the Toy Story series. The Disney-Pixar film Planes belongs to the wider Cars-inspired world but was produced by Disneytoon Studios rather than being a Pixar Cars sequel.