Circuit/System Description
WARNING: This page is about a different car, the 2008 Suzuki Swift +, 2008 Pontiac Wave, and 2008 Chevrolet Aveo. However, it is still accessible from the selected car via links, so may be relevant.
The engine control module (ECM) continuously compares the commanded spark timing to the actual spark timing. The ECM uses the crankshaft position (CKP) sensor and the camshaft position (CMP) sensor in order to calculate the actual spark timing.