Diagnosing electron-controlled gasoline engine default by exhaust gas sensor

The default of ignition system, fuel supply system, electricity system and mechanical mechanism of gasoline engine with carburetor may be diagnosed by secondary ignition wave displayed on automotive oscilloscope, but the running condition ofelectron-controlled engine with three way catalytic converter must be understood only by means of waveform of exhaust gas sensor instead of secondary ignition.If A/F deviates from its theoretical value(14.7), three way catalytic converter's capability to reduce CO, HC and NO_x emissions will rapidly drop.The exhaust gas sensor installed on exhaust gas pipe measures A/F according to oxygen concentration in exhaust gas, and sends feedback signal to ECU in order that A/F converges on its theoretical value.This paper discuses how to analyze electron-controlled engine trouble and its causes using waveform of exhaust gas sensor.