Apparatus detecting abnormality of exhaust system of internal combustion engine

摘要

An engine ECU executes a program including the steps of: detecting an air intake; subtracting an air fuel ratio detected by an upstream air fuel ratio sensor from that detected by a downstream air fuel ratio sensor; using the calculated air fuel ratio difference to determine a range for a lower GA range; determining a range for a higher GA range; and determining from the combination of the determined ranges of the lower and higher GA ranges whether a section A's exhaust system operates normally or has abnormality.