Air-fuel ratio control system for internal combustion engines

摘要

An air-fuel ratio control system for an internal combustion engine detects a central value of an output from a first exhaust gas component concentration sensor arranged in an exhaust passage at a location upstream of a catalytic converter and having an output characteristic which is substantially proportional to the concentration of a component in the exhaust gases. The central value is corrected based on the output from the first exhaust gas component concentration sensor, when an output from a second exhaust gas concentration sensor arranged downstream of the catalytic converter falls within a predetermined range. The output from the first exhaust gas component concentration sensor is corrected based on the corrected central value. An air-fuel ratio of a mixture supplied to the engine is corrected based on the corrected output value from the first exhaust gas component concentration sensor.