Engine self-diagnosis apparatus and control apparatus

Abstract

There is disclosed an apparatus in which changes of linear A/F sensor or engine response characteristics can be detected with high precision in a broad range during operation of an engine. The apparatus includes a controller 50 for controlling an air/fuel ratio of each cylinder of a multiple cylinder engine, and a linear A/F sensor 28 for emitting an output which is proportional to the air/fuel ratio of an exhaust tube assembly. The air/fuel ratio of a specific cylinder is changed by a predetermined amount, a vibration component amplitude or a frequency component based on an engine rotation number is extracted from a signal obtained from the linear A/F sensor 28, and the response characteristics of an air/fuel ratio detector or the engine are detected from the amplitude or a power of the frequency component.

Dependencies are inferred from the claim text.