Circuit Description

In order to detect engine misfire at higher engine speeds, the Engine Control Module (ECM) must know of any variation between the crankshaft sensor pulses. Most variations are due to the machining of the crankshaft reluctor wheel. However, other sources of variation are also possible. A Crankshaft Position (CKP) system variation learning procedure must be performed any time a change is made to the crankshaft sensor to crankshaft relationship of if the ECM is replaced or reprogrammed. The ECM measures the variations and then calculates compensation factors needed to enable the ECM to accurately detect engine misfire at all speeds and loads. A scan tool must be used to command the ECM to learn these variations. If for any reason the ECM is unable to learn these variations or they are out of an acceptable range, the ECM will set Diagnostic Trouble Code (DTC) P0315. An ECM that has not had the CKP system variation learning procedure performed due to replacement or reprogramming will also set DTC P0315.