Circuit Description

WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

This ignition system does not use a conventional Camshaft Position (CMP) sensor that detects valve train position. The Ignition Control Module (ICM) detects when No. 1 or No. 3 cylinder has fired on its compression stroke using sensing circuitry integrated within each coil. The sensing circuit detects the polarity and the strength of the secondary voltage output, the higher output is always at the event cylinder. The ICM sends a CMP sensor signal to the Engine Control Module (ECM) based on the voltage difference between the event and waste cylinder firing energy. This system is called compression sense ignition. By monitoring the CMP and Crankshaft Position (CKP) signals, the ECM can accurately time the operation of the fuel injectors. If the ECM receives an intermittent CMP sensor signal from the ICM, the CMP Resync Counter on the scan tool will increment. When the ECM cannot use the information from the CMP sensor signal, DTC P0340 will set.