Note. For circuit reference, see WIRING DIAGRAMS article.
Circuit Description
PCM uses information from Crankshaft Position (CKP) sensor and Camshaft Position (CMP) sensor to determine when an engine misfire is occurring. By monitoring changes in crankshaft rotation for each cylinder, PCM counts individual misfire events. MIL illuminates when misfire rate equals or exceeds a predetermined count. A misfire rate that is high enough can cause catalytic converter to overheat under certain driving conditions. MIL will flash when conditions for catalytic converter overheating are present.