System Description

The engine control module (ECM) uses information from the crankshaft position (CKP) sensor and the camshaft position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the ECM is able to detect individual misfire events. A misfire rate that is high enough can cause overheating and damage to the 3-way catalytic converter (TWC) under certain driving conditions. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for TWC damage are present. If the ECM detects a misfire rate sufficient to cause emission levels to exceed a predetermined value, and the ECM is able to determine that a specific cylinder is misfiring, the DTC for that cylinder sets.