Patent ID: 7387011
Filing Date: 2008-06-17
Classification: F01N,F02D

Abstract:
1. A deterioration diagnosis system for an exhaust gas, comprising: an exhaust gas sensor disposed in an exhaust pipe of an internal combustion engine; and a diagnosis means for diagnosing a deterioration of the exhaust gas based on a lean-direction responsiveness characteristic of the exhaust gas sensor and a rich-direction responsiveness characteristic of the exhaust gas sensor, the lean-direction responsiveness representing a responsiveness characteristic of the exhaust gas sensor in a case that an air-fuel ratio detected by the exhaust gas sensor is controlled in such a manner as to be varied in a lean direction, the rich-direction responsiveness representing a responsiveness characteristic of the exhaust gas sensor in a case that the air-fuel ratio detected by the exhaust gas sensor is controlled in such a manner as to be varied in a rich direction, wherein the diagnosis means determines whether the exhaust gas sensor deteriorates based on at least one of the lean-direction responsiveness characteristic and the rich-direction responsiveness characteristic, and on a comparison result between the lean-direction responsiveness characteristic and the rich-direction responsiveness characteristic.