Circuit/System Description
WARNING: This page is about a different car, the 2020 Buick Regal TourX, 2020 Buick Regal, 2019 Buick Regal TourX, and 2019 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.
The internal fault detection is handled inside the control module. No external circuit diagnosis is involved.