For those changing major within the CPSLO College of Engineering, materials, manufacturing, and general engineering are the three majors with a 2.000 GPA requirement. Other majors have higher GPA requirements. See https://eadvise.calpoly.edu/changing-majors/within-the-college-of-engineering
In general, admission selectivity of a major (whether frosh entry, transfer entry, declaration of major, or change of major) is mainly based on popularity of the major relative to the instructional capacity of the major.