Patent ID: 6901741
Filing Date: 2005-06-07
Classification: F01N,F02D,Y02T

Abstract:
1. A deterioration diagnosis method of an air/fuel ratio sensor for use with an internal combustion engine which burns an air/fuel mixture of fuel injected by an injector and air, and discharges combustion gas through an exhaust passage as exhaust gas, the engine comprising a catalytic converter provided in the exhaust passage and having an oxygen storage function, wherein the air/fuel ratio sensor is disposed in the exhaust passage upstream of the catalytic converter for detecting an air/fuel ratio of the air-fuel mixture, the deterioration diagnosis method comprising: determining whether a fuel cut, during which fuel is not injected by the fuel injector while the engine is running, has been executed or not; controlling a fuel injection amount of the fuel injector only immediately after an execution of a fuel cut to cause the engine to be operated under an alternating application of a rich air/fuel ratio and a non-rich air/fuel ratio; and performing a diagnosis of deterioration in the air/fuel ratio sensor based on a variation in the air/fuel ratio detected by the air/fuel ratio sensor during the period in which the engine is operated under the alternating application of the rich air/fuel ratio and the non-rich air/fuel ratio.