Circuit/System Description
WARNING: This page is about a different car, the 2007 GMC Sierra, 2007 GMC Cab & Chassis Sierra, 2007 Chevrolet Silverado, and 2007 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The engine control module (ECM) monitors the crankshaft position (CKP) and the camshaft position (CMP) signals to determine if they are synchronized. If both signals are not observed by the ECM within a narrow time window, the ECM will determine that an error has occurred.