Page 216 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

198 Methods for Monitoring and Diagnosing the Eficiency of Catalytic Converters

Output signals produced by all sensors are fed to a control unit which contains a
microcomputer. By analyzing information possessed by the output signals given by such
sensors, the control unit controls the injectors to adjust the amount of fuel fed to each
combustion chamber of the engine. That is, the so-called feedback control for the air-fuel ratio
is carried out by usage of the information signals from the upstream and downstream
oxygen sensors 1 and 2.

In addition, the control unit carries out a catalytic converter deterioration diagnosis. That is,
when it is judged that the catalytic converter is deteriorated to a certain degree, an alarm lamp
is lit.

alarm

Unit (ECU)

Fig. 89 (from US5644912)