Circuit/System Description
WARNING: This page is about a different car, the 2019 Chevrolet Malibu. However, it is still accessible from the selected car via links, so may be relevant.
For an overview of the component/system, refer to:Camshaft Actuator System Description
The ECM compares the signals of the crankshaft position sensor and both camshaft position sensors to detect if the signals are out of sync.